diff --git a/Gemfile b/Gemfile
index 53c501c4b..e42693f30 100644
--- a/Gemfile
+++ b/Gemfile
@@ -41,6 +41,9 @@ gem 'rqrcode'
 gem "html-pipeline", "~> 2.13.2"
 gem "sanitize", "~> 6.0"
 
+# Triggering of Webhooks
+gem "rest-client", "~> 2.1"
+
 # Optional gem for LDAP authentication
 group :ldap do
   gem 'net-ldap', '~> 0.17.0'
diff --git a/app/assets/images/icons.svg b/app/assets/images/icons.svg
index f100919e3..62384e3f1 100644
--- a/app/assets/images/icons.svg
+++ b/app/assets/images/icons.svg
@@ -547,6 +547,11 @@
       <path d="M10 12a2 2 0 1 0 4 0a2 2 0 0 0 -4 0"/>
       <path d="M21 12c-2.4 4 -5.4 6 -9 6c-3.6 0 -6.6 -2 -9 -6c2.4 -4 5.4 -6 9 -6c3.6 0 6.6 2 9 6"/>
     </symbol>
+    <symbol viewBox="0 0 24 24" stroke-linecap="round" stroke-linejoin="round" id="icon--webhook">
+      <path d="M4.876 13.61a4 4 0 1 0 6.124 3.39h6"/>
+      <path d="M15.066 20.502a4 4 0 1 0 1.934 -7.502c-.706 0 -1.424 .179 -2 .5l-3 -5.5"/>
+      <path d="M16 8a4 4 0 1 0 -8 0c0 1.506 .77 2.818 2 3.5l-3 5.5"/>
+    </symbol>
     <symbol viewBox="0 0 24 24" stroke-linecap="round" stroke-linejoin="round" id="icon--wiki-page">
       <path d="M6 4h11a2 2 0 0 1 2 2v12a2 2 0 0 1 -2 2h-11a1 1 0 0 1 -1 -1v-14a1 1 0 0 1 1 -1m3 0v18"/>
       <path d="M13 8l2 0"/>
diff --git a/app/controllers/webhooks_controller.rb b/app/controllers/webhooks_controller.rb
new file mode 100644
index 000000000..d5eb98581
--- /dev/null
+++ b/app/controllers/webhooks_controller.rb
@@ -0,0 +1,59 @@
+# frozen_string_literal: true
+
+class WebhooksController < ApplicationController
+  self.main_menu = false
+
+  before_action :require_login
+  before_action :find_webhook, only: [:edit, :update, :destroy]
+
+  require_sudo_mode :create, :update, :destroy
+
+  def index
+    @webhooks = webhooks.order(:url)
+  end
+
+  def new
+    @webhook = Webhook.new
+  end
+
+  def edit
+  end
+
+  def create
+    @webhook = webhooks.build(webhook_params)
+    if @webhook.save
+      redirect_to webhooks_path
+    else
+      render :new
+    end
+  end
+
+  def update
+    if @webhook.update(webhook_params)
+      redirect_to webhooks_path
+    else
+      render :edit
+    end
+  end
+
+  def destroy
+    @webhook.destroy
+    redirect_to webhooks_path
+  end
+
+  private
+
+  def webhook_params
+    params.require(:webhook).permit(:url, :secret, :active, events: [], project_ids: [])
+  end
+
+  def find_webhook
+    @webhook = webhooks.find(params[:id])
+  rescue ActiveRecord::RecordNotFound
+    render_404
+  end
+
+  def webhooks
+    User.current.webhooks
+  end
+end
diff --git a/app/jobs/webhook_job.rb b/app/jobs/webhook_job.rb
new file mode 100644
index 000000000..a3be1a4ce
--- /dev/null
+++ b/app/jobs/webhook_job.rb
@@ -0,0 +1,16 @@
+# frozen_string_literal: true
+
+class WebhookJob < ApplicationJob
+  def perform(hook_id, payload_json)
+    if hook = Webhook.find_by_id(hook_id)
+      if hook.user&.active?
+        User.current = hook.user
+        hook.call payload_json
+      else
+        Rails.logger.debug { "WebhookJob: user with id=#{hook.user_id} is not active" }
+      end
+    else
+      Rails.logger.debug { "WebhookJob: couldn't find hook with id=#{hook_id}" }
+    end
+  end
+end
diff --git a/app/models/issue.rb b/app/models/issue.rb
index 34f02b300..ee317b006 100644
--- a/app/models/issue.rb
+++ b/app/models/issue.rb
@@ -130,6 +130,10 @@ class Issue < ApplicationRecord
   after_create_commit :add_auto_watcher
   after_commit :create_parent_issue_journal
 
+  after_create_commit  ->{ Webhook.trigger('issue.created', self) }
+  after_update_commit  ->{ Webhook.trigger('issue.updated', self) }
+  after_destroy_commit ->{ Webhook.trigger('issue.deleted', self) }
+
   # Returns a SQL conditions string used to find all issues visible by the specified user
   def self.visible_condition(user, options={})
     Project.allowed_to_condition(user, :view_issues, options) do |role, user|
diff --git a/app/models/project.rb b/app/models/project.rb
index 89a83b202..e13f55a55 100644
--- a/app/models/project.rb
+++ b/app/models/project.rb
@@ -60,6 +60,8 @@ class Project < ApplicationRecord
                           :class_name => 'IssueCustomField',
                           :join_table => "#{table_name_prefix}custom_fields_projects#{table_name_suffix}",
                           :association_foreign_key => 'custom_field_id'
+  has_and_belongs_to_many :webhooks
+
   # Default Custom Query
   belongs_to :default_issue_query, :class_name => 'IssueQuery'
 
diff --git a/app/models/user.rb b/app/models/user.rb
index 496084ceb..f41f654e1 100644
--- a/app/models/user.rb
+++ b/app/models/user.rb
@@ -102,6 +102,8 @@ class User < Principal
   has_one :api_token, lambda {where "#{table.name}.action='api'"}, :class_name => 'Token'
   has_many :email_addresses, :dependent => :delete_all
   has_many :reactions, dependent: :delete_all
+  has_many :webhooks, dependent: :destroy
+
   belongs_to :auth_source
 
   scope :logged, lambda {where("#{User.table_name}.status <> #{STATUS_ANONYMOUS}")}
diff --git a/app/models/webhook.rb b/app/models/webhook.rb
new file mode 100644
index 000000000..b36abdd4c
--- /dev/null
+++ b/app/models/webhook.rb
@@ -0,0 +1,111 @@
+# frozen_string_literal: true
+
+require 'rest-client'
+
+class Webhook < ApplicationRecord
+  Executor = Struct.new(:url, :payload, :secret) do
+    # @return [RestClient::Response] if the POST request was successful
+    # @raise [RestClient::Exception, Exception] a `RestClient::Exception` if an
+    #   unexpected (i.e. non-successful) response status was set; it may contain
+    #   the server response. For connection errors, we may raise any other
+    #   exception.
+    def call
+      # DNS and therefore destination IPs might have changed since the record was saved, so check the URL, again.
+      raise URI::BadURIError unless WebhookEndpointValidator.safe_webhook_uri?(url)
+
+      headers = { accept: '*/*', content_type: :json, user_agent: 'Redmine' }
+      if secret.present?
+        headers['X-Redmine-Signature-256'] = compute_signature
+      end
+      Rails.logger.debug { "Webhook: POST #{url}" }
+      RestClient.post url, payload, headers
+    end
+
+    # Computes the HMAC signature for the given payload and secret.
+    # https://docs.github.com/en/webhooks/using-webhooks/validating-webhook-deliveries
+    def compute_signature
+      'sha256=' + OpenSSL::HMAC.hexdigest(OpenSSL::Digest.new('sha256'), secret, payload)
+    end
+  end
+
+  belongs_to :user
+  has_and_belongs_to_many :projects
+
+  validates :url, presence: true, webhook_endpoint: true, length: { maximum: 2000 }
+  validates :secret, length: { maximum: 255 }, allow_blank: true
+  validate :check_events_array
+
+  serialize :events, coder: YAML, type: Array
+
+  scope :active, -> { where(active: true) }
+
+  before_validation ->(hook){ hook.projects = hook.projects.to_a.select{|p| p.visible?(hook.user) } }
+
+  # Triggers the given event for the given object, scheduling qualifying hooks
+  # to be called.
+  def self.trigger(event, object)
+    hooks_for(event, object).each do |hook|
+      payload = hook.payload(event, object)
+      WebhookJob.perform_later(hook.id, payload.to_json)
+    end
+  end
+
+  # Finds hooks for the given event and object.
+  # Returns an array of hooks that are active, have the given event in their list
+  # of events, and whose user can see the object.
+  #
+  # Object must have a project_id and respond to visible?(user)
+  def self.hooks_for(event, object)
+    Webhook.active
+      .joins("INNER JOIN projects_webhooks on projects_webhooks.webhook_id = webhooks.id")
+      .eager_load(:user)
+      .where(users: { status: User::STATUS_ACTIVE }, projects_webhooks: { project_id: object.project_id })
+      .to_a.select do |hook|
+      hook.events.include?(event) && object.visible?(hook.user)
+    end
+  end
+
+  def setable_projects
+    Project.visible
+  end
+
+  def setable_events
+    WebhookPayload::EVENTS
+  end
+
+  def setable_event_names
+    setable_events.map{|type, actions| actions.map{|action| "#{type}.#{action}"}}.flatten
+  end
+
+  # computes the payload. this happens when the hook is triggered, and the
+  # payload is stored as part of the hook job definition.
+  # event must be of the form 'type.action' (like 'issue.created')
+  def payload(event, object)
+    WebhookPayload.new(event, object, user).to_h
+  end
+
+  # POSTs the given payload to the hook URL, returns true if successful, false otherwise.
+  #
+  # logs any unsuccessful hook calls, but does not raise
+  def call(payload_json)
+    Executor.new(url, payload_json, secret).call
+    true
+  rescue => e
+    Rails.logger.warn { "Webhook Error: #{e.message} (#{e.class})\n#{e.backtrace.join "\n"}" }
+    false
+  end
+
+  private
+
+  def check_events_array
+    unless events.is_a?(Array)
+      errors.add(:events, :invalid)
+      return
+    end
+
+    events.reject!(&:blank?)
+    if (events - setable_event_names).any?
+      errors.add(:events, :invalid)
+    end
+  end
+end
diff --git a/app/models/webhook_payload.rb b/app/models/webhook_payload.rb
new file mode 100644
index 000000000..fd0af9171
--- /dev/null
+++ b/app/models/webhook_payload.rb
@@ -0,0 +1,101 @@
+# frozen_string_literal: true
+
+# Webhook payload
+class WebhookPayload
+  attr_accessor :event, :object, :user
+
+  def initialize(event, object, user)
+    self.event = event
+    self.object = object
+    self.user = user
+  end
+
+  EVENTS = {
+    issue: %w[created updated deleted]
+  }
+
+  def to_h
+    type, action = event.split('.')
+    if EVENTS[type.to_sym].include?(action)
+      send("#{type}_payload", action)
+    else
+      raise ArgumentError, "invalid event: #{event}"
+    end
+  end
+
+  private
+
+  def issue_payload(action)
+    issue = object
+    if issue.current_journal.present?
+      journal = issue.journals.visible(user).find_by_id(issue.current_journal.id)
+    end
+    ts = case action
+         when 'created'
+           issue.created_on
+         when 'deleted'
+           Time.now
+         else
+           journal&.created_on || issue.updated_on
+         end
+    h = {
+      type: event,
+      timestamp: ts.iso8601,
+      data: {
+        issue: ApiRenderer.new("app/views/issues/show.api.rsb", user).to_h(issue: issue)
+      }
+    }
+    if action == 'updated' && journal.present?
+      h[:data][:journal] = journal_payload(journal)
+    end
+    h
+  end
+
+  def journal_payload(journal)
+    {
+      id: journal.id,
+      created_on: journal.created_on.iso8601,
+      notes: journal.notes,
+      user: {
+        id: journal.user.id,
+        name: journal.user.name,
+      },
+      details: journal.visible_details(user).map do |d|
+        {
+          property: d.property,
+          prop_key: d.prop_key,
+          old_value: d.old_value,
+          value: d.value,
+        }
+      end
+    }
+  end
+
+  # given a path to an API template (relative to RAILS_ROOT), renders it and returns the resulting hash
+  class ApiRenderer
+    include ApplicationHelper
+    include CustomFieldsHelper
+    attr_accessor :path, :params, :user
+
+    DummyRequest = Struct.new(:params)
+
+    def initialize(path, user, params = nil)
+      self.path = path
+      self.user = user
+      self.params = params || {}
+    end
+
+    def to_h(**ivars)
+      req = DummyRequest.new(params)
+      api = Redmine::Views::Builders::Json.new(req, nil)
+      ivars.each { |k, v| instance_variable_set :"@#{k}", v }
+      original_user = User.current
+      begin
+        User.current = self.user
+        instance_eval(File.read(Rails.root.join(path)), path, 1)
+      ensure
+        User.current = original_user
+      end
+    end
+  end
+end
diff --git a/app/views/webhooks/_form.html.erb b/app/views/webhooks/_form.html.erb
new file mode 100644
index 000000000..ab927f7f9
--- /dev/null
+++ b/app/views/webhooks/_form.html.erb
@@ -0,0 +1,44 @@
+<%= error_messages_for @webhook %>
+
+<div class="splitcontent">
+  <div class="splitcontentleft">
+    <div class="box tabular">
+      <p><%= f.text_field :url, required: true, size: 60 %>
+        <em class="info"><%= l :webhook_url_info %></em>
+      </p>
+      <p>
+        <%= f.text_field :secret %>
+        <em class="info"><%= raw l :webhook_secret_info_html %></em>
+      </p>
+      <p><%= f.check_box :active %></p>
+    </div>
+
+    <h3><%= l :label_webhook_events %></h3>
+    <div class="box tabular" id="events">
+    <% @webhook.setable_events.keys.sort.each do |type| %>
+      <fieldset id="<%= type %>_events"><legend><%= toggle_checkboxes_link("##{type}_events\ input") %><%= l_or_humanize(type, prefix: 'webhook_events_') %></legend>
+        <% @webhook.setable_events[type].each do |action| %>
+          <% name = "#{type}.#{action}" %>
+          <label class="floating">
+            <%= check_box_tag 'webhook[events][]', name, @webhook.events.include?(name), id: "webhook_events_#{name}" %>
+            <%= l_or_humanize(name.tr('.', '_'), :prefix => 'webhook_events_') %>
+          </label>
+        <% end %>
+        </fieldset>
+    <% end %>
+    <br /><%= check_all_links 'events' %>
+    <%= hidden_field_tag 'webhook[events][]', '' %>
+    </div>
+  </div>
+
+  <div class="splitcontentright">
+    <fieldset class="box" id="webhook_project_ids"><legend><%= toggle_checkboxes_link("#webhook_project_ids input[type=checkbox]") %><%= l(:label_project_plural) %></legend>
+      <% project_ids = @webhook.project_ids.to_a %>
+      <%= render_project_nested_lists(@webhook.setable_projects) do |p|
+        content_tag('label', check_box_tag('webhook[project_ids][]', p.id, project_ids.include?(p.id), :id => nil) + ' ' + h(p))
+      end %>
+      <%= hidden_field_tag('webhook[project_ids][]', '', :id => nil) %>
+    </fieldset>
+
+  </div>
+</div>
diff --git a/app/views/webhooks/edit.html.erb b/app/views/webhooks/edit.html.erb
new file mode 100644
index 000000000..4afb7b0c3
--- /dev/null
+++ b/app/views/webhooks/edit.html.erb
@@ -0,0 +1,6 @@
+<h2><%= l :label_webhook_edit %></h2>
+
+<%= labelled_form_for @webhook, html: { method: :patch } do |f| %>
+  <%= render :partial => 'form', :locals => { :f => f } %>
+  <%= submit_tag l(:button_save) %>
+<% end %>
diff --git a/app/views/webhooks/index.html.erb b/app/views/webhooks/index.html.erb
new file mode 100644
index 000000000..9da188a9c
--- /dev/null
+++ b/app/views/webhooks/index.html.erb
@@ -0,0 +1,35 @@
+<div class="contextual">
+  <%= link_to sprite_icon('add', l(:label_webhook_new)), new_webhook_path, class: 'icon icon-add' %>
+</div>
+
+<%= title l :label_webhook_plural %>
+
+<% if @webhooks.any? %>
+<div class="autoscroll">
+<table class="list">
+  <thead><tr>
+    <th><%= l :field_active %></th>
+    <th><%= l :label_url %></th>
+    <th><%= l :label_webhook_events %></th>
+    <th><%= l :label_project_plural %></th>
+    <th></th>
+  </tr></thead>
+  <tbody>
+  <% @webhooks.each do |webhook| %>
+    <tr id="webhook_<%= webhook.id %>" class="<%= cycle("odd", "even") %>">
+      <td><%= webhook.active ? l(:general_text_Yes) : l(:general_text_No) %></td>
+      <td><%= truncate webhook.url, length: 40 %></td>
+      <td><%= safe_join webhook.events.map{|e| content_tag :code, e }, ', ' %></td>
+      <td><%= safe_join webhook.projects.visible.map{|p| link_to_project(p) }, ', ' %></td>
+      <td class="buttons">
+        <%= link_to sprite_icon('edit', l(:button_edit)), edit_webhook_path(webhook), class: 'icon icon-edit' %>
+        <%= link_to sprite_icon('del', l(:button_delete)), webhook_path(webhook), :data => {:confirm => l(:text_are_you_sure)}, :method => :delete, :class => 'icon icon-del' %>
+      </td>
+    </tr>
+  <% end %>
+  </tbody>
+</table>
+</div>
+<% else %>
+  <p class="nodata"><%= l(:label_no_data) %></p>
+<% end %>
diff --git a/app/views/webhooks/new.html.erb b/app/views/webhooks/new.html.erb
new file mode 100644
index 000000000..50359f320
--- /dev/null
+++ b/app/views/webhooks/new.html.erb
@@ -0,0 +1,7 @@
+<h2><%= l :label_webhook_new %></h2>
+
+<%= labelled_form_for @webhook, url: webhooks_path do |f| %>
+  <%= render :partial => 'webhooks/form', locals: { f: f } %>
+  <%= submit_tag l(:button_create) %>
+  <%= link_to l(:button_cancel), webhooks_path %>
+<% end %>
diff --git a/config/configuration.yml.example b/config/configuration.yml.example
index c528d764e..4e8444ca9 100644
--- a/config/configuration.yml.example
+++ b/config/configuration.yml.example
@@ -224,6 +224,19 @@ default:
   # false: switches to default common mark where two or more spaces are required
   # common_mark_enable_hardbreaks: true
 
+  # Webhooks
+  #
+  # An optional list of hosts and/or IP addresses and/or IP networks which
+  # should NOT be valid as webhook targets. You can add your internal IPs and
+  # hostnames here to avoid possible SSRF attacks.
+  # webhook_blocklist:
+  #   - 10.0.0.0/8
+  #   - 172.16.0.0/12
+  #   - 192.168.0.0/16
+  #   - fc00::/7
+  #   - example.org
+  #   - "*.example.com"
+
 # specific configuration options for production environment
 # that overrides the default ones
 production:
diff --git a/config/icon_source.yml b/config/icon_source.yml
index 1e4c2ae09..c3edb9beb 100644
--- a/config/icon_source.yml
+++ b/config/icon_source.yml
@@ -241,4 +241,6 @@
 - name: loader
   svg: loader-2
 - name: hourglass
-  svg: hourglass
\ No newline at end of file
+  svg: hourglass
+- name: webhook
+  svg: webhook  
\ No newline at end of file
diff --git a/config/locales/de.yml b/config/locales/de.yml
index c4ea072d6..7aeae1768 100644
--- a/config/locales/de.yml
+++ b/config/locales/de.yml
@@ -845,6 +845,17 @@ de:
   label_yesterday: gestern
   label_default_query: Standardabfrage
   label_progressbar: Fortschrittsbalken
+  label_webhook_plural: Webhooks
+  label_webhook_new: Neuer Webhook
+  label_webhook_edit: Webhook bearbeiten
+  label_webhook_events: Ereignisse
+
+  webhook_events_issue: Aufgaben
+  webhook_events_issue_created: Aufgabe angelegt
+  webhook_events_issue_updated: Aufgabe bearbeitet
+  webhook_events_issue_deleted: Aufgabe gelöscht
+  webhook_url_info: Redmine sendet einen POST-Request an diese URL, wenn eines der gewählten Ereignisse in einem der ausgewählten Projekte eintritt.
+  webhook_secret_info_html: Wenn gesetzt, wird Redmine mit jedem Request eine Hash-Signatur im X-Redmine-Signature-256 header übermitteln, die zur Authentifizierung des Requests herangezogen werden kann.
 
   mail_body_account_activation_request: "Ein neuer Benutzer (%{value}) hat sich registriert. Sein Konto wartet auf Ihre Genehmigung:"
   mail_body_account_information: Ihre Konto-Informationen
diff --git a/config/locales/en.yml b/config/locales/en.yml
index f67d2d2f3..5385ad02d 100644
--- a/config/locales/en.yml
+++ b/config/locales/en.yml
@@ -1171,6 +1171,17 @@ en:
   label_oauth_admin_access: Administration
   label_oauth_application_plural: Applications
   label_oauth_authorized_application_plural: Authorized applications
+  label_webhook_plural: Webhooks
+  label_webhook_new: New webhook
+  label_webhook_edit: Edit webhook
+  label_webhook_events: Events
+
+  webhook_events_issue: Issues
+  webhook_events_issue_created: Issue created
+  webhook_events_issue_updated: Issue updated
+  webhook_events_issue_deleted: Issue deleted
+  webhook_url_info: Redmine will send a POST request to this URL whenever one of the selected events occurs in one of the selected projects.
+  webhook_secret_info_html: If provided, Redmine will use this to create a hash signature that is sent with each delivery as the value of the X-Redmine-Signature-256 header.  
 
   button_login: Login
   button_submit: Submit
diff --git a/config/routes.rb b/config/routes.rb
index 7a683c938..df48e19e9 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -35,6 +35,8 @@ Rails.application.routes.draw do
   match 'account/activate', :to => 'account#activate', :via => :get
   get 'account/activation_email', :to => 'account#activation_email', :as => 'activation_email'
 
+  resources :webhooks, only: [:index, :new, :create, :edit, :update, :destroy]
+
   match '/news/preview', :controller => 'previews', :action => 'news', :as => 'preview_news', :via => [:get, :post, :put, :patch]
   match '/issues/preview', :to => 'previews#issue', :as => 'preview_issue', :via => [:get, :post, :put, :patch]
   match '/preview/text', :to => 'previews#text', :as => 'preview_text', :via => [:get, :post, :put, :patch]
diff --git a/db/migrate/20251007073256_create_webhooks.rb b/db/migrate/20251007073256_create_webhooks.rb
new file mode 100644
index 000000000..07bed0684
--- /dev/null
+++ b/db/migrate/20251007073256_create_webhooks.rb
@@ -0,0 +1,17 @@
+class CreateWebhooks < ActiveRecord::Migration[8.0]
+  def change
+    create_table :webhooks do |t|
+      t.string :url, null: false, limit: 2000
+      t.string :secret
+      t.text :events
+      t.integer :user_id, null: false, index: true
+      t.boolean :active, null: false, default: false, index: true
+      t.timestamps
+    end
+
+    create_table :projects_webhooks do |t|
+      t.integer :project_id, null: false, index: true
+      t.integer :webhook_id, null: false, index: true
+    end
+  end
+end
diff --git a/lib/webhook_endpoint_validator.rb b/lib/webhook_endpoint_validator.rb
new file mode 100644
index 000000000..860a0af6a
--- /dev/null
+++ b/lib/webhook_endpoint_validator.rb
@@ -0,0 +1,172 @@
+# frozen_string_literal: true
+
+require 'uri'
+
+class WebhookEndpointValidator < ActiveModel::EachValidator
+  def validate_each(record, attribute, value)
+    return if value.blank?
+
+    unless self.class.safe_webhook_uri?(value)
+      record.errors.add attribute, :invalid
+    end
+  end
+
+  def self.safe_webhook_uri?(value)
+    uri = value.is_a?(URI) ? value : URI.parse(value)
+    return false if uri.nil?
+
+    return false unless valid_scheme?(uri.scheme)
+    return false unless valid_host?(uri.host)
+    return false unless valid_port?(uri.port)
+
+    true
+  rescue
+    Rails.logger.warn { "URI failed webhook safety checks: #{uri}" }
+    false
+  end
+
+  def self.valid_port?(port)
+    !BAD_PORTS.include?(port)
+  end
+
+  def self.valid_scheme?(scheme)
+    %w[http https].include?(scheme)
+  end
+
+  def self.blocked_hosts
+    @blocked_hosts ||= begin
+      ips = []
+      wildcards = []
+      hosts = []
+
+      Array(Redmine::Configuration['webhook_blocklist']).map(&:to_s).each do |block|
+        # We try to parse the block as an IP address first...
+        ips << IPAddr.new(block)
+      rescue IPAddr::Error
+        # If that failed, we assume it is a (wildcard) hostname
+        if block.start_with?('*.')
+          wildcards << Regexp.escape(block[2..])
+        else
+          hosts << Regexp.escape(block)
+        end
+      end
+
+      regex_parts = []
+      regex_parts << "(?:#{hosts.join('|')})" if hosts.any?
+      regex_parts << "(?:.*\\.)?(?:#{wildcards.join('|')})" if wildcards.any?
+
+      {
+        ips: ips.freeze,
+        host: regex_parts.any? ? /\A(?:#{regex_parts.join('|')})\z/i : nil
+      }.freeze
+    end
+  end
+
+  def self.valid_host?(host)
+    return false if host.blank?
+
+    return false if blocked_hosts[:host]&.match?(host)
+
+    Resolv.each_address(host) do |ip|
+      ipaddr = IPAddr.new(ip)
+      return false if ipaddr.link_local? || ipaddr.loopback?
+      return false if IPAddr.new('224.0.0.0/24').include?(ipaddr) # multicast
+      return false if blocked_hosts[:ips].any? { |net| net.include?(ipaddr) }
+    end
+
+    true
+  end
+
+  # A general port blacklist.  Connections to these ports will not be allowed
+  # unless the protocol overrides.
+  #
+  # This list is to be kept in sync with "bad ports" as defined in the
+  # WHATWG Fetch standard at https://fetch.spec.whatwg.org/#port-blocking
+  #
+  # see also: https://github.com/mozilla/gecko-dev/blob/d55e89d48a8053ce45a74b0ec92c0ff6a9dcc43d/netwerk/base/nsIOService.cpp#L109-L199
+  #
+  BAD_PORTS = Set[
+    1,      # tcpmux
+    7,      # echo
+    9,      # discard
+    11,     # systat
+    13,     # daytime
+    15,     # netstat
+    17,     # qotd
+    19,     # chargen
+    20,     # ftp-data
+    21,     # ftp
+    22,     # ssh
+    23,     # telnet
+    25,     # smtp
+    37,     # time
+    42,     # name
+    43,     # nicname
+    53,     # domain
+    69,     # tftp
+    77,     # priv-rjs
+    79,     # finger
+    87,     # ttylink
+    95,     # supdup
+    101,    # hostriame
+    102,    # iso-tsap
+    103,    # gppitnp
+    104,    # acr-nema
+    109,    # pop2
+    110,    # pop3
+    111,    # sunrpc
+    113,    # auth
+    115,    # sftp
+    117,    # uucp-path
+    119,    # nntp
+    123,    # ntp
+    135,    # loc-srv / epmap
+    137,    # netbios
+    139,    # netbios
+    143,    # imap2
+    161,    # snmp
+    179,    # bgp
+    389,    # ldap
+    427,    # afp (alternate)
+    465,    # smtp (alternate)
+    512,    # print / exec
+    513,    # login
+    514,    # shell
+    515,    # printer
+    526,    # tempo
+    530,    # courier
+    531,    # chat
+    532,    # netnews
+    540,    # uucp
+    548,    # afp
+    554,    # rtsp
+    556,    # remotefs
+    563,    # nntp+ssl
+    587,    # smtp (outgoing)
+    601,    # syslog-conn
+    636,    # ldap+ssl
+    989,    # ftps-data
+    990,    # ftps
+    993,    # imap+ssl
+    995,    # pop3+ssl
+    1719,   # h323gatestat
+    1720,   # h323hostcall
+    1723,   # pptp
+    2049,   # nfs
+    3659,   # apple-sasl
+    4045,   # lockd
+    4190,   # sieve
+    5060,   # sip
+    5061,   # sips
+    6000,   # x11
+    6566,   # sane-port
+    6665,   # irc (alternate)
+    6666,   # irc (alternate)
+    6667,   # irc (default)
+    6668,   # irc (alternate)
+    6669,   # irc (alternate)
+    6679,   # osaut
+    6697,   # irc+tls
+    10080  # amanda
+  ].freeze
+end
diff --git a/test/functional/webhooks_controller_test.rb b/test/functional/webhooks_controller_test.rb
new file mode 100644
index 000000000..418eb76d6
--- /dev/null
+++ b/test/functional/webhooks_controller_test.rb
@@ -0,0 +1,73 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class WebhooksControllerTest < Redmine::ControllerTest
+  fixtures :projects, :users, :email_addresses, :user_preferences, :members, :member_roles, :roles,
+           :groups_users,
+           :trackers, :projects_trackers,
+           :enabled_modules,
+           :versions,
+           :issue_statuses, :issue_categories, :issue_relations, :workflows,
+           :enumerations,
+           :issues, :journals, :journal_details
+
+  setup do
+    @project = Project.find 'ecookbook'
+    @dlopper = User.find_by_login 'dlopper'
+    @issue = @project.issues.first
+    @hook = create_hook
+    @other_hook = create_hook user: User.find_by_login('admin'), url: 'https://example.com/other/hook'
+    @request.session[:user_id] = @dlopper.id
+  end
+
+  test "should require login" do
+    @request.session[:user_id] = nil
+    get :index
+    assert_redirected_to '/login?back_url=http%3A%2F%2Ftest.host%2Fwebhooks'
+  end
+
+  test "should get index" do
+    get :index
+    assert_response :success
+    assert_select 'td', text: @hook.url
+    assert_select 'td', text: @other_hook.url, count: 0
+  end
+
+  test "should get new" do
+    get :new
+    assert_response :success
+  end
+
+  test "should create webhook" do
+    assert_difference 'Webhook.count' do
+      post :create, params: { webhook: { url: 'https://example.com/new/hook', events: %w(issue.created), project_ids: [@project.id] } }
+    end
+    assert_redirected_to webhooks_path
+  end
+
+  test "should get edit" do
+    get :edit, params: { id: @hook.id }
+    assert_response :success
+  end
+
+  test "should update webhook" do
+    patch :update, params: { id: @hook.id, webhook: { url: 'https://example.com/updated/hook' } }
+    assert_redirected_to webhooks_path
+    assert_equal 'https://example.com/updated/hook', @hook.reload.url
+  end
+
+  test 'edit should not find hook of other user' do
+    get :edit, params: { id: @other_hook.id }
+    assert_response :not_found
+  end
+
+  private
+
+  def create_hook(url: 'https://example.com/some/hook',
+                  user: User.find_by_login('dlopper'),
+                  events: %w(issue.created issue.updated),
+                  projects: [Project.find('ecookbook')])
+    Webhook.create!(url: url, user: user, events: events, projects: projects)
+  end
+end
diff --git a/test/unit/lib/webhook_endpoint_validator_test.rb b/test/unit/lib/webhook_endpoint_validator_test.rb
new file mode 100644
index 000000000..426316567
--- /dev/null
+++ b/test/unit/lib/webhook_endpoint_validator_test.rb
@@ -0,0 +1,82 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class WebhookEndpointValidatorTest < ActiveSupport::TestCase
+  class TestModel
+    include ActiveModel::Validations
+    attr_accessor :url
+
+    def initialize(url)
+      self.url = url
+    end
+
+    validates :url, webhook_endpoint: true
+  end
+
+  setup do
+    WebhookEndpointValidator.class_eval do
+      @blocked_hosts = nil
+    end
+  end
+
+  test "should validate url" do
+    Redmine::Configuration.with('webhook_blocklist' => ['*.example.org', '10.0.0.0/8', '192.168.0.0/16']) do
+      %w[
+        mailto:user@example.com
+        foobar
+        example.com
+        file://example.com
+        https://x.example.org/
+        http://x.example.org/
+      ].each do |url|
+        assert_not WebhookEndpointValidator.safe_webhook_uri?(url), "#{url} should be invalid"
+        record = TestModel.new url
+        assert_not record.valid?
+        assert record.errors[:url].any?
+      end
+
+      assert WebhookEndpointValidator.safe_webhook_uri? 'https://acme.com/some/webhook?foo=bar'
+      record = TestModel.new 'https://acme.com/some/webhook?foo=bar'
+      assert record.valid?, record.errors.inspect
+    end
+  end
+
+  test "should validate ports" do
+    %w[
+      http://example.com:22
+      http://example.com:1
+    ].each do |url|
+      assert_not WebhookEndpointValidator.safe_webhook_uri?(url), "#{url} should be invalid"
+    end
+    %w[
+      http://example.com
+      http://example.com:80
+      http://example.com:443
+      http://example.com:8080
+    ].each do |url|
+      assert WebhookEndpointValidator.safe_webhook_uri? url
+    end
+  end
+
+  test "should validate ip addresses" do
+    Redmine::Configuration.with('webhook_blocklist' => ['*.example.org', '10.0.0.0/8', '192.168.0.0/16']) do
+      %w[
+        127.0.0.0
+        127.0.0.1
+        10.0.0.0
+        10.0.1.0
+        169.254.1.9
+        192.168.2.1
+        224.0.0.1
+        ::1/128
+        fe80::/10
+      ].each do |ip|
+        assert_not WebhookEndpointValidator.safe_webhook_uri? ip
+        h = TestModel.new "http://#{ip}"
+        assert_not h.valid?, "IP #{ip} should be invalid"
+        assert h.errors[:url].any?
+      end
+    end
+  end
+end
diff --git a/test/unit/webhook_payload_test.rb b/test/unit/webhook_payload_test.rb
new file mode 100644
index 000000000..feaa501df
--- /dev/null
+++ b/test/unit/webhook_payload_test.rb
@@ -0,0 +1,40 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+
+class WebhookPayloadTest < ActiveSupport::TestCase
+  include ActiveJob::TestHelper
+
+  fixtures :projects, :users, :trackers, :projects_trackers, :versions,
+           :issue_statuses, :issue_categories, :issue_relations,
+           :enumerations, :issues, :journals, :journal_details
+
+  setup do
+    @dlopper = User.find_by_login 'dlopper'
+    @project = Project.find 'ecookbook'
+    @issue = @project.issues.first
+  end
+
+  test "issue update payload should contain journal" do
+    @issue.init_journal(@dlopper)
+    @issue.subject = "new subject"
+    @issue.save
+    p = WebhookPayload.new('issue.updated', @issue, @dlopper)
+    assert h = p.to_h
+    assert_equal 'issue.updated', h[:type]
+    assert j = h.dig(:data, :journal)
+    assert_equal 'Dave Lopper', j[:user][:name]
+    assert i = h.dig(:data, :issue)
+    assert_equal 'new subject', i[:subject], i.inspect
+  end
+
+  test "should compute payload of deleted issue" do
+    @issue.destroy
+    p = WebhookPayload.new('issue.deleted', @issue, @dlopper)
+    assert h = p.to_h
+    assert_equal 'issue.deleted', h[:type]
+    assert_nil h.dig(:data, :journal)
+    assert i = h.dig(:data, :issue)
+    assert_equal @issue.subject, i[:subject], i.inspect
+  end
+end
diff --git a/test/unit/webhook_test.rb b/test/unit/webhook_test.rb
new file mode 100644
index 000000000..05c4729a4
--- /dev/null
+++ b/test/unit/webhook_test.rb
@@ -0,0 +1,167 @@
+# frozen_string_literal: true
+
+require 'test_helper'
+require 'pp'
+
+class WebhookTest < ActiveSupport::TestCase
+  include ActiveJob::TestHelper
+
+  fixtures :projects, :users, :email_addresses, :user_preferences, :members, :member_roles, :roles,
+           :groups_users,
+           :trackers, :projects_trackers,
+           :enabled_modules,
+           :versions,
+           :issue_statuses, :issue_categories, :issue_relations, :workflows,
+           :enumerations,
+           :issues, :journals, :journal_details
+
+  setup do
+    # Set ActiveJob to use the test adapter
+    @original_adapter = ActiveJob::Base.queue_adapter
+    ActiveJob::Base.queue_adapter = :test
+
+    @project = Project.find 'ecookbook'
+    @dlopper = User.find_by_login 'dlopper'
+    @issue = @project.issues.first
+    WebhookEndpointValidator.class_eval do
+      @blocked_hosts = nil
+    end
+  end
+
+  teardown do
+    # Restore the original adapter
+    ActiveJob::Base.queue_adapter = @original_adapter
+  end
+
+  test "should validate url" do
+    Redmine::Configuration.with('webhook_blocklist' => ['*.example.org', '10.0.0.0/8', '192.168.0.0/16']) do
+      %w[
+        mailto:user@example.com
+        https://x.example.org/
+        https://example.org/
+        https://x.example.org/foo/bar?a=b
+        foobar
+        example.com
+        https://10.1.0.12/
+      ].each do |url|
+        hook = Webhook.new(url: url)
+        assert_not hook.valid?, "URL '#{url}' should be invalid"
+        assert hook.errors[:url].any?
+      end
+    end
+  end
+
+  test "should validate secret length" do
+    hook = Webhook.new secret: 'abdc' * 100
+    assert_not hook.valid?
+    assert hook.errors[:secret].any?
+  end
+
+  test "should validate events" do
+    Webhook.new.setable_event_names.each do |event|
+      h = create_hook events: [event]
+      assert h.persisted?
+    end
+    hook = Webhook.new(events: ['issue.created', 'invalid.event'])
+    assert_not hook.valid?
+    assert hook.errors[:events].any?
+    assert_raise(ActiveRecord::SerializationTypeMismatch){ Webhook.new(events: 'issue.created') }
+  end
+
+  test "should clean up project list on save" do
+    h = create_hook
+    assert_equal [@project], h.projects
+    @project.memberships.destroy_all
+    @project.update is_public: false
+
+    h.reload
+    h.save
+    h.reload
+    assert_equal [], h.projects
+  end
+
+  test "should check ip address at run time" do
+    Redmine::Configuration.with('webhook_blocklist' => ['*.example.org', '10.0.0.0/8', '192.168.0.0/16']) do
+      %w[
+        127.0.0.0
+        127.0.0.1
+        10.0.0.0
+        10.0.1.0
+        169.254.1.9
+        192.168.2.1
+        224.0.0.1
+        ::1/128
+        fe80::/10
+      ].each do |ip|
+        h = Webhook.new url: "http://#{ip}"
+        assert_not h.valid?, "IP #{ip} should be invalid"
+        assert h.errors[:url].any?
+      end
+    end
+  end
+
+  test "should find hooks for issue" do
+    hook = create_hook
+    assert @issue.visible?(hook.user)
+    assert_equal [hook], Webhook.hooks_for('issue.created', @issue)
+    assert_equal [], Webhook.hooks_for('issue.deleted', @issue)
+    @issue.update_column :project_id, 99
+    assert_equal [], Webhook.hooks_for('issue.created', @issue)
+  end
+
+  test "should not find inactive hook" do
+    hook = create_hook active: false
+    assert @issue.visible?(hook.user)
+    assert_equal [], Webhook.hooks_for('issue.created', @issue)
+  end
+
+  test "should not find hook of inactive user" do
+    admin = User.find_by_login 'admin'
+    hook = create_hook user: admin
+    assert_equal [hook], Webhook.hooks_for('issue.created', @issue)
+    admin.update_column :status, 3
+    assert_equal [], Webhook.hooks_for('issue.created', @issue)
+  end
+
+  test "should find hook for deleted issue" do
+    hook = create_hook events: ['issue.deleted']
+    @issue.destroy
+    assert_equal [hook], Webhook.hooks_for('issue.deleted', @issue)
+  end
+
+  test "schedule should enqueue jobs for hooks" do
+    hook = create_hook
+    assert_enqueued_jobs 1 do
+      assert_enqueued_with(job: WebhookJob) do
+        Webhook.trigger('issue.created', @issue)
+      end
+    end
+  end
+
+  test "should not enqueue job for inactive hook" do
+    hook = create_hook active: false
+    assert_no_enqueued_jobs do
+      Webhook.trigger('issue.created', @issue)
+    end
+  end
+
+  test "should compute payload" do
+    hook = create_hook
+    payload = hook.payload('issue.created', @issue)
+    assert_equal 'issue.created', payload[:type]
+    assert_equal @issue.id, payload.dig(:data, :issue, :id)
+  end
+
+  test "should compute correct signature" do
+    # we're implementing the same signature mechanism as GitHub, so might as well re-use their
+    # example. https://docs.github.com/en/webhooks/using-webhooks/validating-webhook-deliveries
+    e = Webhook::Executor.new('https://example.com', 'Hello, World!', "It's a Secret to Everybody")
+    assert_equal "sha256=757107ea0eb2509fc211221cce984b8a37570b6d7586c22c46f4379c8b043e17", e.compute_signature
+  end
+
+  private
+
+  def create_hook(url: 'https://example.com/some/hook', user: User.find_by_login('dlopper'), projects: [Project.find('ecookbook')], events: ['issue.created'], active: true)
+    Webhook.create!(url: url, user: user, projects: projects, events: events, active: active)
+  end
+end