Board Thread:Support Requests - Getting Technical/@comment-1084762-20160128212956/@comment-1251315-20160128214359

You need to remove any code you have in MediaWiki:Chat-welcome-message, as well as delete MediaWiki:Chat.js/load.js on the wiki, as this import method no longer works and was disabled due to security issues. This change was made many months ago, you should probably try to keep up-to-date with changes made to Wikia through the Technical Updates blog.

You can see how to import customisations into the Chat here: Help:Custom Chat Javascript/CSS