An issue was discovered in MediaWiki before 1.35.12, 1.36.x through 1.39.x before 1.39.5, and 1.40.x before 1.40.1. There is XSS in youhavenewmessagesmanyusers and youhavenewmessages i18n messages. This is related to MediaWiki:Youhavenewmessagesfromusers. Reference: https://phabricator.wikimedia.org/T340221
Created mediawiki tracking bugs for this issue: Affects: fedora-all [bug 2247804]