CVE-2026-33548: MantisBT has Stored HTML Injection / XSS when displaying Tags in Timeline
Improper escaping of tag names retrieved from History in Timeline (myviewpage.php) allows an attacker to inject HTML and, if CSP settings permit, achieve execution of arbitrary JavaScript, when displaying a tag that has been renamed or deleted.
Impact Cross-site scripting (XSS).
Patches f32787c14d4518476fe7f05f992dbfe6eaccd815
Workarounds Edit offending History entries (using SQL) Wrap $this->tagname in a stringhtmlspecialchars() call in IssueTagTimelineEvent::html()
Credits MantisBT thanks Vishal Shukla for discovering and responsibly reporting the issue.
Other sources
Mantis Bug Tracker (MantisBT) is an open source issue tracker. In version 2.28.0, improper escaping of tag names retrieved from History in Timeline (myviewpage.php) allows an attacker to inject HTML and, if CSP settings permit, achieve execution of arbitrary JavaScript, when displaying a tag that has been renamed or deleted. Version 2.28.1 contains a patch. Workarounds include editing offending History entries (using SQL) and wrapping $this->tagname in a stringhtmlspecialchars() call in IssueTagTimelineEvent::html().
— MITRE