Open WebUI versions 0.6.33 up to 0.11.3 contain a stored cross‑site scripting vulnerability in the citation embed_url field. When a user stores a javascript: URL, it is later opened in a victim’s browser via window.open, executing client‑side script within the victim’s session. The primary impact is theft of the locally stored authentication token, granting the attacker full control over the victim’s account. The weakness is classified as CWE‑79 and exposes confidentiality and integrity of user sessions. Based on the description, it is inferred that the attacker must craft a shared chat embedding the malicious citation, and the victim must click the link for the script to run.

Open WebUI from the open‑webui vendor, specifically any installation of the software in the version range 0.6.33 through 0.11.3 is impacted; later releases contain the fix.

The CVSS score of 8.5 classifies this flaw as high severity. No EPSS score is available and it is not listed in the CISA KEV catalog, but the exploitation path is straightforward: an authenticated user can store the malicious URL and share it with others; a victim who clicks the link will have the attacker’s script executed, giving the attacker the session token. The lack of an EPSS score does not mitigate the urgency, as the attack requires only normal user privileges and the ability to publish the crafted citation.