Open WebUI has stored XSS via the HTML renedering view

Exploitation

No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.

CVSS

7.7 · CVSS:3.1/AV:N/AC:H/PR:L/UI:R/S:C/C:H/I:H/A:N

EPSS

• CVE-2026-45303: 0.22% estimated exploitation activity in the next 30 days; percentile 13.31 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.

As published by the source; long descriptions are shortened.

Summary Through the HTML rendering view, scripts can be injected and executed. The finding resulted from a penetration test for a customer. It is suspected that the root cause of the issue lies within the core of Open WebUI, which is why it is being reported as a security issue here. Tested on Open WebUI 0.5.4. Details The frontend provides a function to visualize the HTML content of a current chat. The content is embedded in an iFrame with the following sandbox directive: sandbox="allow-scripts allow-forms allow-same-origin" This means that the content is placed in a sandbox but with permission to execute scripts and access the parent’s data (e.g., local storage). As a result, only a few functions are restricted (e.g., displaying an alert box), but in effect, the sandbox attribute is largely nullified. PoC If an HTML document containing a script is included in the chat, this script will be embedded in the view and executed. This can be achieved with a message like the following: By…

Published by the source

14 May 2026, 20:16 UTC

Last modified by the source

13 Jul 2026, 16:42 UTC

Source last checked

26 Oct 2026, 13:41 UTC

1. Revision 2 · amended · 26 Oct 2026

   Amended from ghsa record GHSA-4vrc-m9ch-6m3r

2. Revision 1 · created · 24 Oct 2026

   Published from osv record GHSA-4vrc-m9ch-6m3r

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# Patch Next advisory brief: CVE-2026-45303

Advisory: Open WebUI has stored XSS via the HTML renedering view
IDs: CVE-2026-45303, GHSA-4vrc-m9ch-6m3r
Record: https://patchnext.com/advisories/cve-2026-45303 (revision 2, source checked 26 Oct 2026, 13:41 UTC)
Inventory: none attached. This brief comes from a public page and does not say whether any deployment is affected.
Severity: High (CVSS 7.7)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: open-webui 0.6.5. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI open-webui: affected < 0.6.5; fixed in 0.6.5

## Suggested inspection (read-only)
- `python -m pip show open-webui`: prints the installed version. Run with the environment that serves production active.

## Supported action
Upgrade each affected component to a fixed version on its release line. For a transitive dependency, upgrade the parent package or add an override or constraint, then regenerate the lockfile. Redeploy every environment that ran an affected version.

## Required regression checks
- Run the test suite and a production build.
- Exercise the features that depend on open-webui.
- Repeat the inspection and confirm that only fixed versions remain installed.

## Rollback considerations
- Keep the previous lockfile and deployment artifact. Rolling back reinstates the vulnerable version, so apply any documented mitigation while you fix forward.

## Unresolved questions
- Which deployments run an affected version?
- Exploitation status can change. Check again before lowering the priority.
- Mark the work resolved only after the fixed version is verified in production.

## Sources
- Verified: https://osv.dev/vulnerability/GHSA-4vrc-m9ch-6m3r (OSV record GHSA-4vrc-m9ch-6m3r lists affected ranges: PyPI open-webui >=0 <0.6.5 (fixed))
- Verified: https://github.com/advisories/GHSA-4vrc-m9ch-6m3r (GitHub-reviewed advisory GHSA-4vrc-m9ch-6m3r lists affected ranges: PyPI open-webui >=0 <0.6.5)

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