According https://www.mediawiki.org/wiki/Extension:RawMsg: "This extension has not been maintained for some time, and no longer supports recent releases of MediaWiki."

Furthermore, this is not something we want on the MediaWiki SaaS, as it allows anybody to inject malicious JS code to any page (MediaWiki requires editinterface right to edit JS files, but with RawMsg, it's possible to put JS code anywhere).

Plan is to find the role of the extension and offer replacement.