XWiki Platform Mentions UI vulnerable to Cross-site Scripting

XWiki Platform Mentions UI is a user interface for mentioning users in wiki content for XWiki Platform, a generic wiki platform. Starting in version 12.5-rc-1 and prior to versions 13.10.6 and 14.4, it's possible to store Javascript or groovy scripts in a mention, macro anchor, or reference field. The stored code is executed by anyone visiting the page with the mention. This issue has been patched on XWiki 14.4 and 13.10.6. As a workaround, one may update `XWiki.Mentions.MentionsMacro` and edit the `Macro code` field of the `XWiki.WikiMacroClass` XObject.