Summary
When cloning an issue originating from a Project other than the current one, the clone form (bug_report_page.php) prepends the source Project name before the category selector without proper escaping, allowing an attacker able to to inject HTML if they can set the Project's name (which typically requires manager or administrator access level).
Workarounds
Make sure Project names do not contain any HTML tags.
Credits
Thanks to Vishal Shukla for discovering and responsibly reporting the issue.
The vulnerability was also identified and independently reported by @siunam321 (Tang Cheuk Hei), prior to this Advisory's publication.
Impact
Cross-site scripting (XSS).
This is mitigated by Content Security Policy which restricts scripts execution.
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
- df22697ae497ddd93f3d9132fdf4979db8d081cd
Frequently Asked Questions
- What is CVE-2026-34463? CVE-2026-34463 is a high-severity cross-site scripting (XSS) vulnerability in mantisbt/mantisbt (composer), affecting versions <= 2.28.1. It is fixed in 2.28.2. 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-2026-34463? mantisbt/mantisbt (composer) versions <= 2.28.1 is affected.
- Is there a fix for CVE-2026-34463? Yes. CVE-2026-34463 is fixed in 2.28.2. Upgrade to this version or later.
- Is CVE-2026-34463 exploitable, and should I be worried? Whether CVE-2026-34463 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-2026-34463 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-2026-34463? Upgrade
mantisbt/mantisbtto 2.28.2 or later.