silverstripe/framework security advisory

CVE-2026-54720: XSS attack through media embed in silverstripe/framework

CVE-2026-54720 is a medium-severity XSS vulnerability in the PHP package silverstripe/framework (CVSS 5.4), published 1 July 2026. It is fixed in 6.2.2; earlier versions are affected. It can be exploited without an account.

medium 5.4 published 2026-07-01 · updated 2026-10-25

Affected versions: < 6.2.2
Fixed in: 6.2.2
Newest release: 6.3.2
Severity: Medium · CVSS 5.4
Type: Cross-site scripting (XSS)
CWE-79
Exploited in the wild: Not on the CISA KEV list
checked 2026-11-04

Is your silverstripe/framework version affected?

Run composer show silverstripe/framework in your project, then enter the version. We check it against this and every other known silverstripe/framework advisory.

Who can exploit CVE-2026-54720

Access: No account. Anyone who can send a request to an app that uses the affected code.
Interaction: A user also has to do something, such as open a link or a page the attacker prepared.

CVSS vector (scored by GitHub): CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:U/C:L/I:L/A:N

Your app is only exposed if it uses the affected part of silverstripe/framework. The advisory below says which part that is. If you are not sure, upgrade anyway: it costs less than finding out.

How to fix CVE-2026-54720 in silverstripe/framework

Find the installed version: composer show silverstripe/framework. If you never required it yourself, composer why silverstripe/framework shows which package pulls it in.
Update it: composer update silverstripe/framework --with-all-dependencies. You need 6.2.2 or newer.
If Composer will not go that high, your composer.json constraint is holding it back. Widen it (for example "silverstripe/framework": "^6.2.2" if you can take that version), or upgrade the package that requires it.
Run composer audit. It reads the same advisory data and should no longer list CVE-2026-54720.
Commit composer.lock and deploy it. On the server, run composer install --no-dev from the lock file, not composer update.

If you cannot upgrade yet

General hardening for XSS issues while the upgrade waits. None of it replaces the fix.

Escape output in your own templates and add a Content-Security-Policy that blocks inline scripts.
Limit who can save the content the advisory names (for example rich text, SVG or form fields).
If your app does not use the affected feature, note that in your audit, but still plan the upgrade.

The CVE-2026-54720 advisory

Silverstripe Framework is a PHP framework which powers the Silverstripe CMS. In versions prior to 6.2.2, the "Insert media from web" functionality in the CMS is vulnerable to XSS from a specially crafted embed. This issue was fixed in version 6.2.2/

Description from the CVE record, published by GitHub (the CVE Numbering Authority), via the NVD entry for CVE-2026-54720. Advisory title: “CVE-2026-54720 - XSS attack through media embed”.

References

GitHub security advisory GHSA-gvrw-qqp5-jgc5 github.com
Silverstripe security advisory www.silverstripe.org

Other silverstripe/framework advisories

CVE-2026-88988: XSS via SVG data URI 2026-10-28
SS-2026-004 - Password reset token account takeover 2026-10-28
CVE-2026-91112: CMS_ACCESS_SecurityAdmin privilege escalation 2026-10-28
CVE-2026-91110: XSS using control bytes 2026-10-28
CVE-2026-88989: Auth bypass GridFieldDetailForm 2026-10-28
CVE-2026-91115: RCE via i18nTextCollectorTask writer parameter 2026-10-28

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Where this data comes from

Affected and fixed versions: the Packagist security advisories API (GitHub Advisory Database and FriendsOfPHP), the same data composer audit uses. Synced 2026-11-03.
Description, score, weakness and references: NIST National Vulnerability Database (NVD), checked 2026-11-04. This product uses data from the NVD API but is not endorsed or certified by the NVD.
Exploited-in-the-wild status: the CISA Known Exploited Vulnerabilities catalog, checked 2026-11-04.
Compiled by Daniel Lasek at Laskyr from the sources above. The summary, “who can exploit it”, “how to fix it” and hardening sections are our plain-English reading of the record and are generated from it. The quoted description is the record's own text. Spot an error? Tell us.