# Open WebUI: Cross-origin postMessage confirmation bypass via action:submit

Advisory record · `GHSA-3vv5-8xxp-4f55`

- **Identifiers:** `GHSA-3vv5-8xxp-4f55` · `CVE-2026-54007` · `PYSEC-2026-2695`
- **State:** Confirmed
- **Severity:** CVSS 7.1 High
- **Critical:** No
- **Weakness (CWE):** [CWE-346](https://cwe.mitre.org/data/definitions/346.html)
- **Tags:** [CWE-346](https://agentprime.io/advisories/tag/cwe-346.md)
- **Published:** 17 Jun 2026
- **Updated:** 20 Jul 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 17 Jun 2026, 14:10 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `open-webui` (PyPI): affected `<0.9.6`; fixed in `0.9.6`

## Machine-written summary

Summary written by Claude Haiku from the source advisory. Not reviewed by a person.

> Open WebUI versions before 0.9.6 let a non-same-origin page send postMessage events that set the chat input text and trigger submission without the usual confirmation dialog. An attacker who lures a logged-in user to a malicious page can cause prompts to be sent under that user's session, including model and tool execution. Upgrade to Open WebUI 0.9.6 or later.

Written 5 Nov 2026.

## Not analysed yet

We haven’t published our analysis of this Advisory yet. Once a person has reviewed it, this page will say what’s vulnerable, what has to be true for your app to be affected, and how to check.

## Severity and exploitation

- 7.1 High, CVSS 4.0: `CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:H/VA:N/SC:N/SI:N/SA:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0023, the 14th percentile, on 10 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:42 UTC: First seen by agentprime
- 31 Oct 2026, 14:42 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-3vv5-8xxp-4f55)

## Sources

- [GitHub Advisory Database: GHSA-3vv5-8xxp-4f55](https://github.com/advisories/GHSA-3vv5-8xxp-4f55)
- [OSV: GHSA-3vv5-8xxp-4f55](https://osv.dev/vulnerability/GHSA-3vv5-8xxp-4f55)
- <https://github.com/open-webui/open-webui/security/advisories/GHSA-3vv5-8xxp-4f55>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-54007>
- <https://github.com/advisories/GHSA-3vv5-8xxp-4f55>
- <https://github.com/open-webui/open-webui>
- <https://github.com/pypa/advisory-database/tree/main/vulns/open-webui/PYSEC-2026-2695.yaml>
- <https://pypi.org/project/open-webui>

Facts on this page come from the GitHub Advisory Database (CC-BY 4.0), OSV and the other sources listed, as published. We don’t reproduce full advisory descriptions, which can contain exploit code.

## Check whether this affects you

A Match means an installed version is in the affected range above. Most don’t affect the app; agentprime hasn’t analysed this one yet.

- With the agentprime MCP server (<https://api.agentprime.io/mcp>), ask your agent to check the project: `check_lockfile` sends a lockfile, `check_packages` a list of installed packages, and both return the Matches and the upgrades that clear them. `get_advisory` returns this record. Setup: <https://agentprime.io/mcp.md>
- In a browser: <https://agentprime.io/check/> reads your lockfile in the browser, never uploading it.
- Whether it touches your code, with file and line: the Claude Code plugin, <https://agentprime.io/plugin.md>
- As JSON: <https://api.agentprime.io/v1/advisories/GHSA-3vv5-8xxp-4f55>, or `POST https://api.agentprime.io/v1/match` with your packages (<https://agentprime.io/api.md>)

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The web page: <https://agentprime.io/advisories/GHSA-3vv5-8xxp-4f55/>. Everything for agents: <https://agentprime.io/llms.txt>.