diff --git a/public/language/en_GB/error.json b/public/language/en_GB/error.json
index 251db61998..fed0c807c9 100644
--- a/public/language/en_GB/error.json
+++ b/public/language/en_GB/error.json
@@ -65,6 +65,7 @@
 	"group-name-too-short": "Group name too short",
 	"group-already-exists": "Group already exists",
 	"group-name-change-not-allowed": "Group name change not allowed",
+	"group-already-member": "You are already part of this group",
 
 	"post-already-deleted": "This post has already been deleted",
 	"post-already-restored": "This post has already been restored",
diff --git a/public/src/client/groups/details.js b/public/src/client/groups/details.js
index c439216d25..0ef47b3fd8 100644
--- a/public/src/client/groups/details.js
+++ b/public/src/client/groups/details.js
@@ -120,7 +120,9 @@ define('forum/groups/details', ['iconSelect', 'vendor/colorpicker/colorpicker',
 					}
 
 					if (settings.name) {
-						ajaxify.go('groups/' + encodeURIComponent(settings.name));
+						var pathname = window.location.pathname;
+						pathname = pathname.substr(1, pathname.lastIndexOf('/'));
+						ajaxify.go(pathname + encodeURIComponent(settings.name));
 					} else {
 						ajaxify.refresh();
 					}
diff --git a/public/src/client/groups/list.js b/public/src/client/groups/list.js
index 3fc76a4962..d4a92ac9aa 100644
--- a/public/src/client/groups/list.js
+++ b/public/src/client/groups/list.js
@@ -10,7 +10,7 @@ define('forum/groups/list', function() {
 		groupsEl.on('click', '.list-cover', function() {
 			var groupName = $(this).parents('[data-group]').attr('data-group');
 
-			ajaxify.go('groups/' + groupName);
+			ajaxify.go('groups/' + encodeURIComponent(groupName));
 		});
 
 		// Group creation
diff --git a/src/database/redis/main.js b/src/database/redis/main.js
index 5157386d3b..9b08e4af65 100644
--- a/src/database/redis/main.js
+++ b/src/database/redis/main.js
@@ -77,6 +77,7 @@ module.exports = function(redisClient, module) {
 	};
 
 	module.deleteAll = function(keys, callback) {
+		callback = callback || function() {};
 		var multi = redisClient.multi();
 		for(var i=0; i<keys.length; ++i) {
 			multi.del(keys[i]);
@@ -91,16 +92,19 @@ module.exports = function(redisClient, module) {
 	};
 
 	module.set = function(key, value, callback) {
+		callback = callback || function() {};
 		redisClient.set(key, value, function(err) {
 			callback(err);
 		});
 	};
 
 	module.increment = function(key, callback) {
+		callback = callback || function() {};
 		redisClient.incr(key, callback);
 	};
 
 	module.rename = function(oldKey, newKey, callback) {
+		callback = callback || function() {};
 		redisClient.rename(oldKey, newKey, function(err, res) {
 			callback(err);
 		});
diff --git a/src/groups.js b/src/groups.js
index 696d8a690f..8f64ea57bd 100644
--- a/src/groups.js
+++ b/src/groups.js
@@ -7,6 +7,7 @@ var async = require('async'),
 	path = require('path'),
 	nconf = require('nconf'),
 	fs = require('fs'),
+	validator = require('validator'),
 
 	user = require('./user'),
 	meta = require('./meta'),
@@ -202,6 +203,9 @@ var async = require('async'),
 				results.base['cover:position'] = '50% 50%';
 			}
 
+			results.base.name = validator.escape(results.base.name);
+			results.base.description = validator.escape(results.base.description);
+			results.base.userTitle = validator.escape(results.base.userTitle);
 			results.base.members = results.users.filter(Boolean);
 			results.base.pending = results.pending.filter(Boolean);
 			results.base.count = numUsers || results.base.members.length;
@@ -611,15 +615,26 @@ var async = require('async'),
 	};
 
 	Groups.requestMembership = function(groupName, uid, callback) {
-		if (parseInt(uid, 10) > 0) {
-			db.setAdd('group:' + groupName + ':pending', uid, callback);
-			plugins.fireHook('action:group.requestMembership', {
-				groupName: groupName,
-				uid: uid
-			});
-		} else {
-			callback(new Error('[[error:not-logged-in]]'));
-		}
+		async.parallel({
+			exists: async.apply(Groups.isMember, uid, groupName),
+			isMember: async.apply(Groups.exists, groupName)
+		}, function(err, checks) {
+			if (!checks.exists) {
+				return callback(new Error('[[error:no-group]]'));
+			} else if (checks.isMember) {
+				return callback(new Error('[[error:group-already-member]]'));
+			}
+
+			if (parseInt(uid, 10) > 0) {
+				db.setAdd('group:' + groupName + ':pending', uid, callback);
+				plugins.fireHook('action:group.requestMembership', {
+					groupName: groupName,
+					uid: uid
+				});
+			} else {
+				callback(new Error('[[error:not-logged-in]]'));
+			}
+		});
 	};
 
 	Groups.acceptMembership = function(groupName, uid, callback) {
diff --git a/src/privileges/categories.js b/src/privileges/categories.js
index 7662ef5913..5ff70730d4 100644
--- a/src/privileges/categories.js
+++ b/src/privileges/categories.js
@@ -143,6 +143,12 @@ module.exports = function(privileges) {
 		}, callback);
 	};
 
+	privileges.categories.rescind = function(privileges, cid, groupName, callback) {
+		async.each(privileges, function(privilege, next) {
+			groups.leave('cid:' + cid + ':privileges:groups:' + privilege, groupName, next);
+		}, callback);
+	};
+
 	privileges.categories.canMoveAllTopics = function(currentCid, targetCid, uid, callback) {
 		async.parallel({
 			isAdministrator: function(next) {