diff --git a/CHANGELOG.md b/CHANGELOG.md
index 9f10d52d6..66985d3e5 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -6,8 +6,10 @@
     * Added `orderBy()` and `limit()` methods to `ObjectCollectionInterface` and its base classes
     * Flex: Added support for custom object index classes (API compatibility break)
     * Added `user-data://` which is a writable stream (`user://data` is not and should be avoided)
-    * Added support for `/action:{$action}` (like task but works without nonce, used only for getting data)
+    * Added support for `/action:{$action}` (like task but used without nonce when only receiving data)
     * Added `onAction.{$action}` event
+    * Added `FormFlash` class to contain AJAX uploaded files in more reliable way
+    * Added `FormFlashFile` class which implements `UploadedFileInterface` from PSR-7
 1. [](#improved)
     * Improve Flex storage
 1. [](#bugfix)
diff --git a/system/src/Grav/Framework/Flex/FlexForm.php b/system/src/Grav/Framework/Flex/FlexForm.php
index 193d87a4a..ab3a84c07 100644
--- a/system/src/Grav/Framework/Flex/FlexForm.php
+++ b/system/src/Grav/Framework/Flex/FlexForm.php
@@ -16,6 +16,7 @@ use Grav\Common\Grav;
 use Grav\Common\Utils;
 use Grav\Framework\Flex\Interfaces\FlexFormInterface;
 use Grav\Framework\Flex\Interfaces\FlexObjectInterface;
+use Grav\Framework\Form\FormFlash;
 use Grav\Framework\Route\Route;
 use Psr\Http\Message\ServerRequestInterface;
 use Psr\Http\Message\UploadedFileInterface;
@@ -36,31 +37,33 @@ class FlexForm implements FlexFormInterface
     private $submitted;
     /** @var string[] */
     private $errors;
-    /** @var Data */
+    /** @var Data|FlexObjectInterface */
     private $data;
-    /** @var UploadedFileInterface[] */
+    /** @var array|UploadedFileInterface[] */
     private $files;
     /** @var FlexObjectInterface */
     private $object;
+    /** @var FormFlash */
+    private $flash;
 
     /**
      * FlexForm constructor.
      * @param string $name
-     * @param FlexObjectInterface|null $object
+     * @param FlexObjectInterface $object
      */
-    public function __construct(string $name = '', FlexObjectInterface $object = null)
+    public function __construct(string $name, FlexObjectInterface $object)
     {
-        $this->reset();
-
-        if ($object) {
-            $this->setObject($object);
-        }
-
         $this->name = $name;
-        $this->id = $this->getName();
+        $this->setObject($object);
+        $this->setId($this->getName());
+        $this->reset();
     }
 
     /**
+     * Get HTML id="..." attribute.
+     *
+     * Defaults to 'flex-[type]-[name]', where 'type' is object type and 'name' is the first parameter given in constructor.
+     *
      * @return string
      */
     public function getId(): string
@@ -69,6 +72,8 @@ class FlexForm implements FlexFormInterface
     }
 
     /**
+     * Sets HTML id="" attribute.
+     *
      * @param string $id
      */
     public function setId(string $id): void
@@ -77,34 +82,10 @@ class FlexForm implements FlexFormInterface
     }
 
     /**
-     * @return string
-     */
-    public function getName(): string
-    {
-        $object = $this->object;
-        $name = $this->name ?: 'object';
-
-        return "flex-{$object->getType(false)}-{$name}";
-    }
-
-
-    /**
-     * @return string
-     */
-    public function getNonceName(): string
-    {
-        return 'nonce';
-    }
-
-    /**
-     * @return string
-     */
-    public function getNonceAction(): string
-    {
-        return 'flex-object';
-    }
-
-    /**
+     * Get unique id for the current form instance. By default regenerated on every page reload.
+     *
+     * This id is used to load the saved form state, if available.
+     *
      * @return string
      */
     public function getUniqueId(): string
@@ -116,6 +97,51 @@ class FlexForm implements FlexFormInterface
         return $this->uniqueid;
     }
 
+    /**
+     * Sets unique form id allowing you to attach the form state to the object for example.
+     *
+     * @param string $uniqueId
+     */
+    public function setUniqueId(string $uniqueId): void
+    {
+        $this->uniqueid = $uniqueId;
+    }
+
+    /**
+     * @return string
+     */
+    public function getName(): string
+    {
+        $object = $this->getObject();
+        $name = $this->name ?: 'object';
+
+        return "flex-{$object->getType(false)}-{$name}";
+    }
+
+    /**
+     * @return string
+     */
+    public function getFormName(): string
+    {
+        return $this->name;
+    }
+
+    /**
+     * @return string
+     */
+    public function getNonceName(): string
+    {
+        return 'form-nonce';
+    }
+
+    /**
+     * @return string
+     */
+    public function getNonceAction(): string
+    {
+        return 'form';
+    }
+
     /**
      * @return string
      */
@@ -125,29 +151,20 @@ class FlexForm implements FlexFormInterface
         return '';
     }
 
-    /**
-     * @return array
-     */
-    public function getButtons(): array
-    {
-        return [
-            [
-                'type' => 'submit',
-                'value' => 'Save'
-            ]
-        ];
-    }
-
     /**
      * @return Data|FlexObjectInterface
      */
     public function getData()
     {
-        if (null === $this->data) {
-            $this->data = $this->getObject();
-        }
+        return $this->data ?? $this->getObject();
+    }
 
-        return $this->data;
+    /**
+     * @return array|UploadedFileInterface[]
+     */
+    public function getFiles(): array
+    {
+        return $this->files;
     }
 
     /**
@@ -160,57 +177,11 @@ class FlexForm implements FlexFormInterface
      */
     public function getValue(string $name)
     {
-        $data = $this->getData();
-        return $data instanceof FlexObject ? $data->getNestedProperty($name) : $data->get($name);
-    }
-
-    /**
-     * @return UploadedFileInterface[]
-     */
-    public function getFiles(): array
-    {
-        return $this->files;
-    }
-
-    /**
-     * @return Route|null
-     */
-    public function getFileUploadAjaxRoute(): ?Route
-    {
-        $object = $this->getObject();
-        if (!method_exists($object, 'route')) {
-            return null;
+        if (null === $this->data) {
+            return $this->getObject()->getNestedProperty($name);
         }
 
-        return $object->route('/edit.json/task:media.upload');
-    }
-
-    /**
-     * @param $field
-     * @param $filename
-     * @return Route|null
-     */
-    public function getFileDeleteAjaxRoute($field, $filename): ?Route
-    {
-        $object = $this->getObject();
-        if (!method_exists($object, 'route')) {
-            return null;
-        }
-
-        return $object->route('/edit.json/task:media.delete');
-    }
-
-    /**
-     * Note: this method clones the object.
-     *
-     * @param FlexObjectInterface $object
-     * @return $this
-     */
-    public function setObject(FlexObjectInterface $object): FlexFormInterface
-    {
-        $this->object = clone $object;
-
-        return $this;
+        return $this->data->get($name);
     }
 
     /**
@@ -218,10 +189,6 @@ class FlexForm implements FlexFormInterface
      */
     public function getObject(): FlexObjectInterface
     {
-        if (!$this->object) {
-            throw new \RuntimeException('FlexForm: Object is not defined');
-        }
-
         return $this->object;
     }
 
@@ -285,26 +252,14 @@ class FlexForm implements FlexFormInterface
             }
 
             $this->files = $files ?? [];
-            $this->data = new Data($this->decodeData($data['data'] ?? []));
+            $this->data = new Data($this->decodeData($data['data'] ?? []), $this->getBlueprint());
             if ($this->getErrors()) {
                 return $this;
             }
 
-            $this->validate();
+            $this->doSubmit($this->data->toArray(), $this->files);
 
             $this->submitted = true;
-
-            $object = clone $this->object;
-            $object->update($this->data->toArray());
-            $object->triggerEvent('onSave');
-
-            if (method_exists($object, 'upload')) {
-                $object->upload($this->files);
-            }
-            $object->save();
-
-            $this->object = $object;
-            $this->valid = true;
         } catch (ValidationException $e) {
             $list = [];
             foreach ($e->getMessages() as $field => $errors) {
@@ -386,6 +341,33 @@ class FlexForm implements FlexFormInterface
         $this->object = $data['object'];
     }
 
+    /**
+     * @return Route|null
+     */
+    public function getFileUploadAjaxRoute(): ?Route
+    {
+        $object = $this->getObject();
+        if (!method_exists($object, 'route')) {
+            return null;
+        }
+
+        return $object->route('/edit.json/task:media.upload');
+    }
+
+    /**
+     * @param $field
+     * @param $filename
+     * @return Route|null
+     */
+    public function getFileDeleteAjaxRoute($field, $filename): ?Route
+    {
+        $object = $this->getObject();
+        if (!method_exists($object, 'route')) {
+            return null;
+        }
+
+        return $object->route('/edit.json/task:media.delete');
+    }
 
     public function getMediaTaskRoute(): string
     {
@@ -405,6 +387,33 @@ class FlexForm implements FlexFormInterface
         return '/' . $this->object->getKey();
     }
 
+    /**
+     * Note: this method clones the object.
+     *
+     * @param FlexObjectInterface $object
+     * @return $this
+     */
+    protected function setObject(FlexObjectInterface $object): FlexFormInterface
+    {
+        $this->object = clone $object;
+
+        return $this;
+    }
+
+    /**
+     * Get flash object
+     *
+     * @return FormFlash
+     */
+    protected function getFlash()
+    {
+        if (null === $this->flash) {
+            $this->flash = new FormFlash($this->getName(), $this->getUniqueId());
+        }
+
+        return $this->flash;
+    }
+
     /**
      * @throws \Exception
      */
@@ -415,6 +424,41 @@ class FlexForm implements FlexFormInterface
         $this->checkUploads($this->files);
     }
 
+    protected function setErrors(array $errors): void
+    {
+        $this->errors = array_merge($this->errors, $errors);
+    }
+
+    protected function setError(string $error): void
+    {
+        $this->errors[] = $error;
+    }
+
+    /**
+     * @param array $data
+     * @param array $files
+     * @throws \Exception
+     */
+    protected function doSubmit(array $data, array $files)
+    {
+        $this->validate();
+
+        $object = clone $this->object;
+        $object->update($data);
+
+        if (method_exists($object, 'triggerEvent')) {
+            $object->triggerEvent('onSave');
+        }
+
+        if (method_exists($object, 'upload')) {
+            $object->upload($files);
+        }
+
+        $object->save();
+
+        $this->object = $object;
+    }
+
     protected function checkUploads(array $files): void
     {
         foreach ($files as $file) {
diff --git a/system/src/Grav/Framework/Flex/FlexObject.php b/system/src/Grav/Framework/Flex/FlexObject.php
index e5cc56018..af38f40c0 100644
--- a/system/src/Grav/Framework/Flex/FlexObject.php
+++ b/system/src/Grav/Framework/Flex/FlexObject.php
@@ -18,6 +18,7 @@ use Grav\Common\Page\Medium\MediumFactory;
 use Grav\Common\Twig\Twig;
 use Grav\Framework\ContentBlock\HtmlBlock;
 use Grav\Framework\Flex\Interfaces\FlexAuthorizeInterface;
+use Grav\Framework\Flex\Interfaces\FlexFormInterface;
 use Grav\Framework\Flex\Traits\FlexAuthorizeTrait;
 use Grav\Framework\Object\Access\NestedArrayAccessTrait;
 use Grav\Framework\Object\Access\NestedPropertyTrait;
@@ -170,7 +171,7 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
     public function getForm(string $name = '')
     {
         if (!isset($this->_forms[$name])) {
-            $this->_forms[$name] = new FlexForm($name, $this);
+            $this->_forms[$name] = $this->createFormObject($name);
         }
 
         return $this->_forms[$name];
@@ -662,4 +663,15 @@ class FlexObject implements FlexObjectInterface, FlexAuthorizeInterface
 
         unset ($elements['storage_key'], $elements['storage_timestamp']);
     }
+
+    /**
+     * This methods allows you to override form objects in child classes.
+     *
+     * @param string $name Form name
+     * @return FlexFormInterface
+     */
+    protected function createFormObject(string $name): FlexFormInterface
+    {
+        return new FlexForm($name, $this);
+    }
 }
diff --git a/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php b/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
index 1a6bc7e46..dedf059dc 100644
--- a/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
+++ b/system/src/Grav/Framework/Flex/Interfaces/FlexFormInterface.php
@@ -31,6 +31,16 @@ interface FlexFormInterface extends \Serializable
      */
     public function setId(string $id): void;
 
+    /**
+     * @return string
+     */
+    public function getUniqueId(): string;
+
+    /**
+     * @param string $uniqueId
+     */
+    public function setUniqueId(string $uniqueId): void;
+
     /**
      * @return string
      */
@@ -47,21 +57,11 @@ interface FlexFormInterface extends \Serializable
      */
     public function getNonceAction(): string;
 
-    /**
-     * @return string
-     */
-    public function getUniqueId(): string;
-
     /**
      * @return string
      */
     public function getAction(): string;
 
-    /**
-     * @return array
-     */
-    public function getButtons() : array;
-
     /**
      * @return Data|FlexObjectInterface
      */
@@ -94,14 +94,6 @@ interface FlexFormInterface extends \Serializable
      */
     public function getFileDeleteAjaxRoute($field, $filename): ?Route;
 
-    /**
-     * Note: this method clones the object.
-     *
-     * @param FlexObjectInterface $object
-     * @return $this
-     */
-    public function setObject(FlexObjectInterface $object): self;
-
     /**
      * @return FlexObjectInterface
      */
@@ -152,20 +144,6 @@ interface FlexFormInterface extends \Serializable
      */
     public function getBlueprint(): Blueprint;
 
-    /**
-     * Implements \Serializable::serialize().
-     *
-     * @return string
-     */
-    public function serialize(): string;
-
-    /**
-     * Implements \Serializable::unserialize().
-     *
-     * @param string $data
-     */
-    public function unserialize($data): void;
-
     /**
      * @return string
      */
diff --git a/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php b/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
index c9a6c7428..2012291d2 100644
--- a/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
+++ b/system/src/Grav/Framework/Flex/Traits/FlexMediaTrait.php
@@ -80,7 +80,7 @@ trait FlexMediaTrait
         }
     }
 
-    public function uploadMediaFile(UploadedFileInterface $uploadedFile, string $filename = null) : void
+    public function uploadMediaFile(UploadedFileInterface $uploadedFile, string $filename = null, string $field = null) : void
     {
         $this->checkUploadedMediaFile($uploadedFile);
 
@@ -121,7 +121,7 @@ trait FlexMediaTrait
         $this->clearMediaCache();
     }
 
-    public function deleteMediaFile(string $filename) : void
+    public function deleteMediaFile(string $filename, string $field = null) : void
     {
         $grav = Grav::instance();
         $language = $grav['language'];
diff --git a/system/src/Grav/Framework/Form/FormFlash.php b/system/src/Grav/Framework/Form/FormFlash.php
new file mode 100644
index 000000000..7396f96ab
--- /dev/null
+++ b/system/src/Grav/Framework/Form/FormFlash.php
@@ -0,0 +1,400 @@
+<?php
+
+/**
+ * @package    Grav\Framework\Form
+ *
+ * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
+ * @license    MIT License; see LICENSE file for details.
+ */
+
+namespace Grav\Framework\Form;
+
+use Grav\Common\Filesystem\Folder;
+use Grav\Common\Grav;
+use Grav\Common\Session;
+use Grav\Common\User\User;
+use RocketTheme\Toolbox\File\YamlFile;
+
+class FormFlash implements \JsonSerializable
+{
+    /** @var string */
+    protected $form;
+    /** @var string */
+    protected $uniqueId;
+    /** @var string */
+    protected $url;
+    /** @var array */
+    protected $user;
+    /** @var array */
+    protected $uploads;
+    /** @var array */
+    protected $uploadObjects;
+    /** @var bool */
+    protected $exists;
+
+    /**
+     * FormFlashObject constructor.
+     * @param string $form
+     * @param string $uniqueId
+     */
+    public function __construct(string $form, $uniqueId = null)
+    {
+        $this->form = $form;
+        $this->uniqueId = $uniqueId;
+
+        $file = $this->getTmpIndex();
+        $this->exists = $file->exists();
+
+        $data = $this->exists ? (array)$file->content() : [];
+        $this->url = $data['url'] ?? null;
+        $this->user = $data['user'] ?? null;
+        $this->uploads = $data['uploads'] ?? [];
+    }
+
+    /**
+     * @return string
+     */
+    public function getFormName() : string
+    {
+        return $this->form;
+    }
+
+    /**
+     * @return string
+     */
+    public function getUniqieId() : string
+    {
+        return $this->uniqueId ?? $this->getFormName();
+    }
+
+    /**
+     * @return bool
+     */
+    public function exists() : bool
+    {
+        return $this->exists;
+    }
+
+    /**
+     * @return $this
+     */
+    public function save() : self
+    {
+        $file = $this->getTmpIndex();
+        $file->save($this->jsonSerialize());
+        $this->exists = true;
+
+        return $this;
+    }
+
+    public function delete() : self
+    {
+        $this->removeTmpDir();
+        $this->uploads = [];
+        $this->exists = false;
+
+        return $this;
+    }
+
+    /**
+     * @return string
+     */
+    public function getUrl() : string
+    {
+        return $this->url ?? '';
+    }
+
+    /**
+     * @param string $url
+     * @return $this
+     */
+    public function setUrl(string $url) : self
+    {
+        $this->url = $url;
+
+        return $this;
+    }
+
+    /**
+     * @return string
+     */
+    public function getUsername() : string
+    {
+        return $this->user['username'] ?? '';
+    }
+
+    /**
+     * @return string
+     */
+    public function getUserEmail() : string
+    {
+        return $this->user['email'] ?? '';
+    }
+
+    /**
+     * @param User|null $user
+     * @return $this
+     */
+    public function setUser(?User $user = null) : self
+    {
+        if ($user && $user->username) {
+            $this->user = [
+                'username' => $user->username,
+                'email' => $user->email
+            ];
+        } else {
+            $this->user = null;
+        }
+
+        return $this;
+    }
+
+
+    /**
+     * @param string $field
+     * @return array
+     */
+    public function getFilesByField(string $field) : array
+    {
+        if (!isset($this->uploadObjects[$field])) {
+            $objects = [];
+            foreach ($this->uploads[$field] ?? [] as $filename => $upload) {
+                $objects[$filename] = new FormFlashFile($field, $upload, $this);
+            }
+            $this->uploadObjects[$field] = $objects;
+        }
+
+        return $this->uploadObjects[$field];
+    }
+
+    /**
+     * @return array
+     */
+    public function getFilesByFields() : array
+    {
+        $list = [];
+        foreach ($this->uploads as $field => $values) {
+            if (strpos($field, '/')) {
+                continue;
+            }
+            $list[$field] = $this->getFilesByField($field);
+        }
+
+        return $list;
+    }
+
+    /**
+     * @return array
+     * @deprecated 1.6 For backwards compatibility only, do not use.
+     */
+    public function getLegacyFiles() : array
+    {
+        $fields = [];
+        foreach ($this->uploads as $field => $files) {
+            if (strpos($field, '/')) {
+                continue;
+            }
+            foreach ($files as $file) {
+                $file['tmp_name'] = $this->getTmpDir() . '/' . $file['tmp_name'];
+                $fields[$field][$file['path'] ?? $file['name']] = $file;
+            }
+        }
+
+        return $fields;
+    }
+
+    /**
+     * @param string $field
+     * @param string $filename
+     * @param array $upload
+     * @return bool
+     */
+    public function uploadFile(string $field, string $filename, array $upload) : bool
+    {
+        $tmp_dir = $this->getTmpDir();
+
+        Folder::create($tmp_dir);
+
+        $tmp_file = $upload['file']['tmp_name'];
+        $basename = basename($tmp_file);
+
+        if (!move_uploaded_file($tmp_file, $tmp_dir . '/' . $basename)) {
+            return false;
+        }
+
+        $upload['file']['tmp_name'] = $basename;
+
+        if (!isset($this->uploads[$field])) {
+            $this->uploads[$field] = [];
+        }
+
+        // Prepare object for later save
+        $upload['file']['name'] = $filename;
+
+        // Replace old file, including original
+        $oldUpload = $this->uploads[$field][$filename] ?? null;
+        if (isset($oldUpload['tmp_name'])) {
+            $this->removeTmpFile($oldUpload['tmp_name']);
+        }
+
+        $originalUpload = $this->uploads[$field . '/original'][$filename] ?? null;
+        if (isset($originalUpload['tmp_name'])) {
+            $this->removeTmpFile($originalUpload['tmp_name']);
+            unset($this->uploads[$field . '/original'][$filename]);
+        }
+
+        // Prepare data to be saved later
+        $this->uploads[$field][$filename] = $upload['file'];
+
+        return true;
+    }
+
+    /**
+     * @param string $field
+     * @param string $filename
+     * @param array $upload
+     * @param array $crop
+     * @return bool
+     */
+    public function cropFile(string $field, string $filename, array $upload, array $crop) : bool
+    {
+        $tmp_dir = $this->getTmpDir();
+
+        Folder::create($tmp_dir);
+
+        $tmp_file = $upload['file']['tmp_name'];
+        $basename = basename($tmp_file);
+
+        if (!move_uploaded_file($tmp_file, $tmp_dir . '/' . $basename)) {
+            return false;
+        }
+
+        $upload['file']['tmp_name'] = $basename;
+
+        if (!isset($this->uploads[$field])) {
+            $this->uploads[$field] = [];
+        }
+
+        // Prepare object for later save
+        $upload['file']['name'] = $filename;
+
+        $oldUpload = $this->uploads[$field][$filename] ?? null;
+        if ($oldUpload) {
+            $originalUpload = $this->uploads[$field . '/original'][$filename] ?? null;
+            if ($originalUpload) {
+                $this->removeTmpFile($oldUpload['tmp_name']);
+            } else {
+                $oldUpload['crop'] = $crop;
+                $this->uploads[$field . '/original'][$filename] = $oldUpload;
+            }
+        }
+
+        // Prepare data to be saved later
+        $this->uploads[$field][$filename] = $upload['file'];
+
+        return true;
+    }
+
+    /**
+     * @param string $field
+     * @param string $filename
+     * @return bool
+     */
+    public function removeFile(string $field, string $filename) : bool
+    {
+        if (!$field || !$filename) {
+            return false;
+        }
+
+        $file = $this->getTmpIndex();
+        if (!$file->exists()) {
+            return false;
+        }
+
+        $upload = $this->uploads[$field][$filename] ?? null;
+        if (null !== $upload) {
+            $this->removeTmpFile($upload['tmp_name'] ?? '');
+        }
+        $upload = $this->uploads[$field . '/original'][$filename] ?? null;
+        if (null !== $upload) {
+            $this->removeTmpFile($upload['tmp_name'] ?? '');
+        }
+
+        // Walk backward to cleanup any empty field that's left
+        unset(
+            $this->uploadObjects[$field][$filename],
+            $this->uploads[$field][$filename],
+            $this->uploadObjects[$field . '/original'][$filename],
+            $this->uploads[$field . '/original'][$filename]
+        );
+        if (empty($this->uploads[$field])) {
+            unset($this->uploads[$field]);
+        }
+        if (empty($this->uploads[$field . '/original'])) {
+            unset($this->uploads[$field . '/original']);
+        }
+
+        return true;
+    }
+
+    /**
+     * @return array
+     */
+    public function jsonSerialize() : array
+    {
+        return [
+            'form' => $this->form,
+            'unique_id' => $this->uniqueId,
+            'url' => $this->url,
+            'user' => $this->user,
+            'uploads' => $this->uploads
+        ];
+    }
+
+    /**
+     * @return string
+     */
+    public function getTmpDir() : string
+    {
+        $grav = Grav::instance();
+
+        /** @var Session $session */
+        $session = $grav['session'];
+
+        $location = [
+            'forms',
+            $session->getId(),
+            $this->uniqueId ?: $this->form
+        ];
+
+        return $grav['locator']->findResource('tmp://', true, true) . '/' . implode('/', $location);
+    }
+
+    /**
+     * @return YamlFile
+     */
+    protected function getTmpIndex() : YamlFile
+    {
+        // Do not use CompiledYamlFile as the file can change multiple times per second.
+        return YamlFile::instance($this->getTmpDir() . '/index.yaml');
+    }
+
+    /**
+     * @param string $name
+     */
+    protected function removeTmpFile(string $name) : void
+    {
+        $filename = $this->getTmpDir() . '/' . $name;
+        if ($name && is_file($filename)) {
+            unlink($filename);
+        }
+    }
+
+    protected function removeTmpDir() : void
+    {
+        $tmpDir = $this->getTmpDir();
+        if (file_exists($tmpDir)) {
+            Folder::delete($tmpDir);
+        }
+    }
+}
diff --git a/system/src/Grav/Framework/Form/FormFlashFile.php b/system/src/Grav/Framework/Form/FormFlashFile.php
new file mode 100644
index 000000000..2cb78d016
--- /dev/null
+++ b/system/src/Grav/Framework/Form/FormFlashFile.php
@@ -0,0 +1,146 @@
+<?php
+
+/**
+ * @package    Grav\Framework\Form
+ *
+ * @copyright  Copyright (C) 2015 - 2018 Trilby Media, LLC. All rights reserved.
+ * @license    MIT License; see LICENSE file for details.
+ */
+
+namespace Grav\Framework\Form;
+
+use Grav\Framework\Psr7\Stream;
+use Psr\Http\Message\StreamInterface;
+use Psr\Http\Message\UploadedFileInterface;
+
+class FormFlashFile implements UploadedFileInterface, \JsonSerializable
+{
+    private $field;
+    private $moved = false;
+    private $upload;
+    private $flash;
+
+    public function __construct(string $field, array $upload, FormFlash $flash)
+    {
+        $this->field = $field;
+        $this->upload = $upload;
+        $this->flash = $flash;
+
+        if ($this->isOk() && (empty($this->upload['tmp_name']) || !file_exists($this->getTmpFile()))) {
+            $this->upload['error'] = \UPLOAD_ERR_NO_FILE;
+        }
+
+        if (!isset($this->upload['size'])) {
+            $this->upload['size'] =  $this->isOk() ? filesize($this->getTmpFile()) : 0;
+        }
+    }
+
+    /**
+     * @return StreamInterface
+     */
+    public function getStream()
+    {
+        $this->validateActive();
+
+        $resource = \fopen($this->getTmpFile(), 'rb');
+
+        return Stream::create($resource);
+    }
+
+    public function moveTo($targetPath)
+    {
+        $this->validateActive();
+
+        if (!\is_string($targetPath) || empty($targetPath)) {
+            throw new \InvalidArgumentException('Invalid path provided for move operation; must be a non-empty string');
+        }
+
+        $this->moved = \copy($this->getTmpFile(), $targetPath);
+
+        if (false === $this->moved) {
+            throw new \RuntimeException(\sprintf('Uploaded file could not be moved to %s', $targetPath));
+        }
+
+        $this->flash->removeFile($this->field, $this->upload['tmp_name']);
+    }
+
+    public function getSize()
+    {
+        return $this->upload['size'];
+    }
+
+    public function getError()
+    {
+        return $this->upload['error'] ?? \UPLOAD_ERR_OK;
+    }
+
+    public function getClientFilename()
+    {
+        return $this->upload['name'] ?? 'unknown';
+    }
+
+    public function getClientMediaType()
+    {
+        return $this->upload['type'] ?? 'application/octet-stream';
+    }
+
+    public function isMoved() : bool
+    {
+        return $this->moved;
+    }
+
+    public function getMetaData() : array
+    {
+        if (isset($this->upload['crop'])) {
+            return ['crop' => $this->upload['crop']];
+        }
+
+        return [];
+    }
+
+    public function getDestination()
+    {
+        return $this->upload['path'];
+    }
+
+    public function jsonSerialize()
+    {
+        return $this->upload;
+    }
+
+    public function __debugInfo()
+    {
+        return [
+            'field:private' => $this->field,
+            'moved:private' => $this->moved,
+            'upload:private' => $this->upload,
+        ];
+    }
+
+    /**
+     * @throws \RuntimeException if is moved or not ok
+     */
+    private function validateActive(): void
+    {
+        if (!$this->isOk()) {
+            throw new \RuntimeException('Cannot retrieve stream due to upload error');
+        }
+
+        if ($this->moved) {
+            throw new \RuntimeException('Cannot retrieve stream after it has already been moved');
+        }
+    }
+
+    /**
+     * @return bool return true if there is no upload error
+     */
+    private function isOk(): bool
+    {
+        return \UPLOAD_ERR_OK === $this->getError();
+    }
+
+    private function getTmpFile() : string
+    {
+        return $this->flash->getTmpDir() . '/' . $this->upload['tmp_name'];
+    }
+}