Gogs's Unauthenticated Jupyter Notebook (ipynb) Sanitizer allows arbitrary data: URIs leading to XSS

Exploitation

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

CVSS 4.0

5.4 · CVSS:4.0/AV:N/AC:L/AT:N/PR:N/UI:P/VC:N/VI:N/VA:N/SC:H/SI:H/SA:N/E:P · score source

EPSS

• CVE-2026-52816: 0.68% estimated exploitation activity in the next 30 days; percentile 52.30 (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 The Jupyter Notebook (ipynb) sanitizer endpoint at POST /-/api/sanitizeipynb allows arbitrary data: URIs without proper restrictions, potentially leading to Cross-Site Scripting (XSS). The endpoint uses bluemonday.UGCPolicy() with p.AllowURLSchemes("data") which permits all data URI schemes including data:text/html, enabling attackers to inject malicious HTML/JavaScript. Additionally, the endpoint has no authentication middleware, allowing any registered user to exploit this vulnerability. Severity High Affected Versions All versions using the vulnerable endpoint Vulnerability Details - CVE ID: (To be assigned) - Entry Point: POST /-/api/sanitizeipynb - Attack Vector: Network - Authentication Required: No (only needs a registered user account) Impact An attacker with a registered user account can: - Send malicious HTML containing data:text/html URIs to the sanitization endpoint - Receive sanitized but attacker-controlled HTML in the response - Execute arbitrary JavaScript in…

Published by the source

23 Jun 2026, 17:33 UTC

Last modified by the source

21 Jul 2026, 13:17 UTC

Source last checked

26 Oct 2026, 15:27 UTC

1. Revision 1 · created · 26 Oct 2026

   Published from ghsa record GHSA-3w28-36p9-w929

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# Patch Next advisory brief: CVE-2026-52816

Advisory: Gogs's Unauthenticated Jupyter Notebook (ipynb) Sanitizer allows arbitrary data: URIs leading to XSS
IDs: CVE-2026-52816, GHSA-3w28-36p9-w929
Record: https://patchnext.com/advisories/cve-2026-52816 (revision 1, source checked 26 Oct 2026, 15:27 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: gogs.io/gogs 0.14.3. A vendor fix does not mean a deployment is fixed.

## Affected components
- Go gogs.io/gogs: affected < 0.14.3; fixed in 0.14.3

## Suggested inspection (read-only)
- Go gogs.io/gogs: check the installed version with your package manager.

## 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 gogs.io/gogs.
- 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://github.com/advisories/GHSA-3w28-36p9-w929 (GitHub-reviewed advisory GHSA-3w28-36p9-w929 lists affected ranges: Go gogs.io/gogs >=0 <0.14.3)

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