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Medium, CVSS 5.4amended

Open WebUI has stored XSS via unsanitized Office/Excel/DOCX file preview rendering ({@html} without DOMPurify)

CVE-2026-45318GHSA-hcwp-82g6-8wxc

What to do

Vendor fix available. Upgrade each affected package to the fixed version on its release line (open-webui 0.9.3), redeploy, then verify what is actually installed.

This page has no inventory attached, so it cannot say whether you are affected. A vendor fix is not proof that your deployment is fixed.

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Affected packages

Sources

Severity and exploitation
Exploitation
No confirmed exploitation recorded. Patch Next marks exploitation only from CISA KEV.
CVSS
5.4 · CVSS:3.1/AV:N/AC:L/PR:L/UI:R/S:C/C:L/I:L/A:N
EPSS
  • CVE-2026-45318: 0.21% estimated exploitation activity in the next 30 days; percentile 11.18 (FIRST EPSS, 2026-11-03). This is a model estimate, not proof of exploitation or customer exposure.
Source description

As published by the source; long descriptions are shortened.

Related advisory This advisory tracks a regression of the original Excel-preview XSS that was publicly disclosed and patched under GHSA-jwf8-pv5p-vhmc (patched in v0.8.0). The same root cause — XLSX.utils.sheettohtml() output rendered via {@html excelHtml} without DOMPurify — was reintroduced sometime after v0.8.0 and is exploitable again as of v0.8.12 and through the version range listed above. This advisory additionally covers the related fileOfficeHtml sink in src/lib/components/chat/FileNav.svelte (lines 458 and 1285) which was not part of the jwf8 advisory's scope. Summary Open WebUI renders user-uploaded Office files (Excel, DOCX) as HTML using Svelte's {@html} directive without DOMPurify sanitization. While the codebase has DOMPurify available and uses it in 9 out of 23 {@html} locations (39%), three file-preview rendering paths bypass it entirely, allowing Stored XSS when a user uploads a malicious document. This is a classic defense propagation failure: the sanitization…

Dates and revisions
Published by the source
Last modified by the source
Source last checked
  1. Revision 2 · amended ·

    Amended from ghsa record GHSA-hcwp-82g6-8wxc

  2. Revision 1 · created ·

    Published from osv record GHSA-hcwp-82g6-8wxc

Agent brief

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# Patch Next advisory brief: CVE-2026-45318

Advisory: Open WebUI has stored XSS via unsanitized Office/Excel/DOCX file preview rendering ({@html} without DOMPurify)
IDs: CVE-2026-45318, GHSA-hcwp-82g6-8wxc
Record: https://patchnext.com/advisories/cve-2026-45318 (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: Medium (CVSS 5.4)
Exploitation: no confirmed exploitation recorded. Patch Next confirms exploitation only from CISA KEV.
Vendor response: Vendor fix available; fixed versions by package: open-webui 0.9.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- PyPI open-webui: affected <= 0.9.2; fixed in 0.9.3

## 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-hcwp-82g6-8wxc (OSV record GHSA-hcwp-82g6-8wxc lists affected ranges: PyPI open-webui >=0 <0.9.3 (fixed))
- Verified: https://github.com/advisories/GHSA-hcwp-82g6-8wxc (GitHub-reviewed advisory GHSA-hcwp-82g6-8wxc lists affected ranges: PyPI open-webui >=0 <=0.9.2)

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