Headline
GHSA-g955-vw6w-v6pp: Citizen vulnerable to stored XSS in sticky header button messages
Summary
The JS implementation for copying button labels to the sticky header in the Citizen skin unescapes HTML characters, allowing for stored XSS through system messages.
Details
In the copyButtonAttributes function in stickyHeader.js, when copying the button labels, the innerHTML of the new element is set to the textContent of the old element:
https://github.com/StarCitizenTools/mediawiki-skins-Citizen/blob/f4cbcecf5aca0ae69966b23d4983f9cb5033f319/resources/skins.citizen.scripts/stickyHeader.js#L29-L41
This unescapes any escaped HTML characters and causes the contents of the system messages to be interpreted as HTML.
PoC
- Edit any of the affected messages (
citizen-share,citizen-view-history,citizen-view-edit,nstab-talk) to the following payload:<img src="" onerror="alert('Sticky Header Button XSS')">. - Visit any mainpage article in the wiki using the Citizen skin.
<img width="495" height="228" alt="image" src="https://github.com/user-attachments/assets/ac75b8e1-b181-4335-9526-17d6b6f8518e" /> <img width="569" height="157" alt="image" src="https://github.com/user-attachments/assets/c052edb9-ff68-4869-9c66-3ec85e7ff68a" />
Impact
This impacts wikis where a group has the editinterface but not the editsitejs user right. By default, this is the case for the sysop group.
Attack vector: More severe the more the remote (logically and physically) an attacker can be in order to exploit the vulnerability.
Attack complexity: More severe for the least complex attacks.
Privileges required: More severe if no privileges are required.
User interaction: More severe when no user interaction is required.
Scope: More severe when a scope change occurs, e.g. one vulnerable component impacts resources in components beyond its security scope.
Confidentiality: More severe when loss of data confidentiality is highest, measuring the level of data access available to an unauthorized user.
Integrity: More severe when loss of data integrity is the highest, measuring the consequence of data modification possible by an unauthorized user.
Availability: More severe when the loss of impacted component availability is highest.