GHSA-4j5h-mvj3-m48v Star Citizen EmbedVideo Extension Stored XSS through wikitext caused by usage of non-reserved data attributes

• Packagist starcitizenwiki/embedvideo: <= 4.0.0 (no fix yet)

Summary The EmbedVideo extension allows adding arbitrary attributes to an HTML element, allowing for stored XSS through wikitext. Details The attributes of an iframe are populated with the value of an unreserved data attribute (`data-iframeconfig`) that can be set via wikitext: https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/blob/440fb331a84b2050f4cc084c1d31d58a1d1c202d/resources/ext.embedVideo.videolink.js#L5-L20 Similar code is also present here: https://github.com/StarCitizenWiki/mediawiki-extensions-EmbedVideo/blob/440fb331a84b2050f4cc084c1d31d58a1d1c202d/resources/modules/iframe.js#L139-L155 It is possible to execute JS through attributes like `onload` or `onmouseenter`. PoC 1. Create a page with the following contents: ```html Click me! ``` 2. Click on the "Click me!" text 3. Click on the "Load video" button below Impact Arbitrary HTML can be inserted into the DOM by any user, allowing for JavaScript to be executed.