Headline
GHSA-prmv-7r8c-794g: Citizen vulnerable to Stored XSS through short descriptions
Summary
Short descriptions set via the ShortDescription extension are inserted as raw HTML by the Citizen skin, allowing any user to insert arbitrary HTML into the DOM by editing a page.
Details
The shortdesc property, which contains unsanitized user input, is retrieved from the OutputPage and returned as the tagline:
https://github.com/StarCitizenTools/mediawiki-skins-Citizen/blob/0d8a44011e02a081618359a1e90f462478e807aa/includes/Components/CitizenComponentPageHeading.php#L249-L251
The tagline is then provided to the template data:
https://github.com/StarCitizenTools/mediawiki-skins-Citizen/blob/0d8a44011e02a081618359a1e90f462478e807aa/includes/Components/CitizenComponentPageHeading.php#L270-L275
The template then inserts the tagline into raw HTML without doing any escaping:
https://github.com/StarCitizenTools/mediawiki-skins-Citizen/blob/0d8a44011e02a081618359a1e90f462478e807aa/templates/PageHeading.mustache#L12
PoC
- Enable Citizen and ShortDescription
- Add
{{SHORTDESC:<img src="" onerror="alert('citizen shortdescription xss')">}}to a page - Visit the page
Impact
Arbitrary HTML can be inserted into the DOM by any user, allowing for JavaScript to be executed.
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.