Summary
Improper escaping of Tag name when deleting it in tag_delete.php allows an attacker to inject HTML and, if CSP settings permit, achieve execution of arbitrary JavaScript.
Workarounds
- Revert commit d6890320752ecf37bd74d11fe14fe7dc12335be9
- Manually edit language files to remove the sprintf placeholder
%1$sfrom $s_tag_delete_message string, for example withsed -r -i '/tag_delete_message/s/.%1\$s.//' -- lang/
Credits
MantisBT hanks Vishal Shukla for discovering and responsibly reporting the issue.
Impact
Cross-site scripting (XSS).
Untrusted input is rendered as active markup in a victim's browser, which can run script in their session. Typical impact: session or credential theft, and actions taken as the user.
Affected versions
Security releases
Kodem intelligence
Severity tells you how bad this could be in the worst case. It does not tell you whether you are exposed. Exploitability and impact are functions of runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A vulnerable package can sit in your dependency tree and never run.
Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter. Kodem's runtime-powered SCA identifies whether this CVE is reachable in your applications.
Remediation advice
80990f43153167c73f11eb4b2bc7108d0c3d6b46
Frequently Asked Questions
- What is CVE-2026-33517? CVE-2026-33517 is a high-severity cross-site scripting (XSS) vulnerability in mantisbt/mantisbt (composer), affecting versions = 2.28.0. It is fixed in 2.28.1. Untrusted input is rendered as active markup in a victim's browser, which can run script in their session.
- Which versions of mantisbt/mantisbt are affected by CVE-2026-33517? mantisbt/mantisbt (composer) versions = 2.28.0 is affected.
- Is there a fix for CVE-2026-33517? Yes. CVE-2026-33517 is fixed in 2.28.1. Upgrade to this version or later.
- Is CVE-2026-33517 exploitable, and should I be worried? Whether CVE-2026-33517 is exploitable in your environment depends on whether the vulnerable code is present and reachable. A CVSS score is a worst-case rating; it does not account for your specific deployment, configuration, or usage patterns. Kodem, an Intelligent Application Security platform, uses runtime intelligence to show which vulnerabilities actually execute in production, so you can focus on the ones that represent real risk. Get a demo
- What actually determines whether CVE-2026-33517 is exploitable, and how bad it is? Exploitability and impact are not fixed properties of a CVE. They depend on runtime truth: whether the vulnerable code is present, reachable, and actually executes in your application. A high CVSS score on a dependency that never runs is not the same as real risk. Kodem, an Intelligent Application Security platform, uses runtime intelligence to reveal which vulnerabilities actually execute in production, so teams prioritize the ones that genuinely matter.
- How do I fix CVE-2026-33517? Upgrade
mantisbt/mantisbtto 2.28.1 or later.