CVE-2025-21612 — starcitizentools/tabber-n…
HIGHFix: StarCitizenTools/mediawiki-extensions-TabberNeue@d8c3db4CVE-2025-21612 is a high-severity (CVSS 8.6) Cross-site Scripting (XSS) vulnerability in starcitizentools/tabber-neue. A fix is available for starcitizentools/tabber-neue — see the affected versions and patch details below.
Cross-site Scripting in TabberTransclude in Extension:TabberNeue
Exploitation Status
Proof-of-concept exploit code exists
- CISA’s SSVC triage found public proof-of-concept exploit code for this CVE, though no confirmed active exploitation.
- A successful exploit gives an attacker total control of the affected component, not partial access.
Exploitation and automatability from CISA’s SSVC triage for CVE-2025-21612.
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2025-21612 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
starcitizentools/tabber-neueReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.
Description
Summary
There are several sources of arbitrary, unescaped user input being used to construct HTML, which allows any user that can edit pages or otherwise render wikitext to XSS other users.
Edit: Only the first XSS can be reproduced in production.
Details
✅ Verified and patched in f229cab099c69006e25d4bad3579954e481dc566
https://github.com/StarCitizenTools/mediawiki-extensions-TabberNeue/blob/2526daa9f8cfdd616c861c8439755cb74a6c8c6e/includes/TabberTransclude.php#L154 This doesn't escape the user-supplied page name when outputting, so an XSS payload as the page name can be used here.
This was caused by d8c3db4e5935476e496d979fb01f775d3d3282e6.
❌ Invalid as MediaWiki parser sanitizes dangerous HTML
https://github.com/StarCitizenTools/mediawiki-extensions-TabberNeue/blob/2526daa9f8cfdd616c861c8439755cb74a6c8c6e/includes/Tabber.php#L160
The documentation for Parser::recursiveTagParse() states that it returns unsafe HTML, and the $content being supplied is from user input.
This was caused by 95351812613e04717f3ad7844cfcc67e4ede4d11.
❌ Invalid as TabberParsoid is not being used
https://github.com/StarCitizenTools/mediawiki-extensions-TabberNeue/blob/2526daa9f8cfdd616c861c8439755cb74a6c8c6e/includes/TabberParsoid.php#L96 This uses unescaped user input as the attribute of an element, thus allowing the user to break out of the attribute or element and injecting arbitrary attributes to the element, or inserting new ones (such as a script tag).
This was caused by 8278e665480f08da635aee383c6b5caaeca26ba3.
PoC
For the first XSS, render the following wikitext (whether it be through saving it to a page and viewing it, or via Special:ExpandTemplates):
<tabbertransclude>
<script>alert(1)</script> | hehe
</tabbertransclude>
For the second XSS, I have given up attempting to reproduce it after over twenty minutes of "surfing through the internals of the MediaWiki parser fishing for an XSS out of this giant contraption as I bring myself deeper and deeper into the cogs of the machine that no one knows how to maintain or fully operate ever since its conception".
For the third XSS, this is unreachable as the class is never used, though it should be fixed anyway (or the file removed).
Impact
Any user with the ability to cause another user to render wikitext (such as viewing a page that the user can edit, or an attacker tricking the victim to click on a link to Special:ExpandTemplates with the malicious wikitext in the wpInput parameter) can XSS said user.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | starcitizentools/tabber-neue | ≥ 1.9.1&&< 2.7.2 | 2.7.2composer require starcitizentools/tabber-neue:^2.7.2 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for starcitizentools/tabber-neue, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update starcitizentools/tabber-neue to 2.7.2 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2025-21612 is resolved across your whole dependency graph.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2025-21612 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2025-21612. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2025-21612 in your dependencies?
O3 Security finds CVE-2025-21612 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.