GHSA-prmv-7r8c-794g

### Summary Short descriptions set via the [ShortDescription extension](https://www.mediawiki.org/wiki/Extension:ShortDescription) 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 1. Enable Citizen and ShortDescription 2. Add `{{SHORTDESC:<img src="" onerror="alert('citizen shortdescription xss')">}}` to a page 3. Visit the page  

### Impact Arbitrary HTML can be inserted into the DOM by any user, allowing for JavaScript to be executed.