The vulnerability is a cross‑origin message handling flaw in the SyncStatsModal component of Open WebUI. An attacker can send unvalidated verify:chat messages from an arbitrary website. When a signed‑in user opens the modal, the malformed message triggers a path‑traversal in the chat ID, redirecting the authenticated stats‑export request to the auths endpoint. The server returns the victim’s JWT, allowing the attacker to hijack the session and gain unrestricted API access. This flaw is classified as CWE‑346, resulting in a complete compromise of confidentiality and integrity for the affected user.

Affected are installations of Open WebUI from version 0.7.0 through 0.11.3 inclusive. Each of those releases contains the vulnerable SyncStatsModal implementation. No additional product versions or vendors are listed. The issue is effective for any user who is signed in and opens the modal, regardless of role.

The CVSS score of 8.6 indicates high severity. The EPSS score is not available, and the vulnerability is not recorded in the CISA KEV catalog. Based on the description, the likely attack vector is client‑side: a malicious website can host a page that targets the vulnerable UI and posts a crafted message. Because the flaw requires only the victim’s signed‑in session, exploitation is straightforward for anyone who can reach the UI. The overall risk to affected deployments is therefore high, especially when the UI is exposed to untrusted networks.