# Silverstripe Framework: Possible XSS attack through media embed

Advisory record · `GHSA-gvrw-qqp5-jgc5`

- **Identifiers:** `GHSA-gvrw-qqp5-jgc5` · `CVE-2026-54720` · `PKSA-x6tz-s6v3-ynk3`
- **State:** Confirmed
- **Severity:** CVSS 5.4 Medium
- **Critical:** No
- **Weakness (CWE):** [CWE-79](https://cwe.mitre.org/data/definitions/79.html)
- **Tags:** [Cross-site scripting (XSS)](https://agentprime.io/advisories/tag/xss.md)
- **Published:** 27 Aug 2026
- **Updated:** 27 Aug 2026
- **Reviewed by a person:** No

Published by the GitHub Advisory Database at 27 Aug 2026, 16:49 UTC. agentprime has not analysed this yet, so whether it affects any app is not known.

## Affected packages

- `silverstripe/framework` (Packagist): affected `<6.2.2`; fixed in `6.2.2`

## Machine-written summary

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

> The Packagist package silverstripe/framework, versions before 6.2.2, is vulnerable to cross-site scripting through the "Insert media from web" function in the CMS, which can be triggered by a specially crafted media embed. The source does not say what privileges an attacker needs or exactly what they can do after exploiting it. Upgrade silverstripe/framework to version 6.2.2 or later, which is the fixed version.

Written 31 Oct 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

- 5.4 Medium, CVSS 3.1: `CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N`, from CNA (GitHub_M)

- **CISA KEV:** Not listed.
- **EPSS:** 0.0026, the 18th percentile, on 15 Nov 2026: FIRST’s estimate of the chance of exploitation in the next 30 days.

## Timeline

- 31 Oct 2026, 14:07 UTC: First seen by agentprime
- 31 Oct 2026, 14:07 UTC: [Confirmed by OSV](https://osv.dev/vulnerability/GHSA-gvrw-qqp5-jgc5)

## Sources

- [GitHub Advisory Database: GHSA-gvrw-qqp5-jgc5](https://github.com/advisories/GHSA-gvrw-qqp5-jgc5)
- [OSV: GHSA-gvrw-qqp5-jgc5](https://osv.dev/vulnerability/GHSA-gvrw-qqp5-jgc5)
- <https://github.com/silverstripe/silverstripe-framework/security/advisories/GHSA-gvrw-qqp5-jgc5>
- <https://nvd.nist.gov/vuln/detail/CVE-2026-54720>
- <https://github.com/silverstripe/silverstripe-framework/pull/11993>
- <https://github.com/silverstripe/silverstripe-framework/commit/1bcb02adfc365c6436dc26ab2f6dd32d97f3979b>
- <https://github.com/FriendsOfPHP/security-advisories/blob/master/silverstripe/framework/CVE-2026-54720.yaml>
- <https://github.com/silverstripe/silverstripe-framework>
- <https://github.com/silverstripe/silverstripe-framework/releases/tag/6.2.2>
- <https://www.silverstripe.org/download/security-releases/cve-2026-54720>

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-gvrw-qqp5-jgc5>, 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-gvrw-qqp5-jgc5/>. Everything for agents: <https://agentprime.io/llms.txt>.