The ScratchSig extension for MediaWiki before version 1.0.1 allows stored Cross-Site Scripting. Using <script> tag inside <scratchsig> tag, attackers with edit permission can execute scripts on visitors' browser. With MediaWiki JavaScript API, this can potentially lead to privilege escalation and/or account takeover. This has been patched in release 1.0.1. This has already been deployed to all Scratch Wikis. No workarounds exist other than disabling the extension completely.