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MEDIUM severity

CVE-2020-9311 — cms

MEDIUM

CVE-2020-9311 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in silverstripe/cms. A fix is available for silverstripe/cms — see the affected versions and patch details below.

Silverstripe CMS XSS Vulnerability

Also known asBIT-silverstripe-2020-9311GHSA-2pw2-qpcp-m47x
Published
Updated
Affected
2 pkgs
Patched
1 / 2
Exploits
None indexed
Exploitation data as of Nov 10, 2026 · OSV.dev, NVD, FIRST.org (EPSS)

EPSS Exploitation Probability

via FIRST.org ↗
0.6%probability of exploitation in next 30 days
Lower Risk0.00%
Lower risk than most CVEs47th percentile — riskier than 47% of all scored CVEsHighest risk
0.00%0.35%0.70%1.06%0.3%0.6%May 26Sep 26Nov 26

Probability of exploitation in the next 30 days, from FIRST.org EPSS.

How urgent is this, really

Where this sits among everything scored

Real-World Exposure

2 pkgs affected
🐘silverstripe/cms🐘silverstripe/framework

Real-time download stats are indexed for npm and PyPI packages. This vulnerability affects Packagist packages — download data is not available via public APIs for these ecosystems.

Description

In SilverStripe through 4.5, malicious users with a valid Silverstripe CMS login (usually CMS access) can craft profile information which can lead to XSS for other users through specially crafted login form URLs.

Affected Packages

2 total 1 fixed
EcosystemPackageVulnerable rangeFix
🐘Packagistsilverstripe/cmsall versionsNo fix
🐘Packagistsilverstripe/framework≥ 3.0.0&&< 3.7.53.7.5composer require silverstripe/framework:^3.7.5

Affected Products

1 product · 1 configurations
Application
silverstripesilverstripe
≥ 3.0.0 && < 3.7.5
range

Detection & mitigation playbook

Open-source dependency

  1. Detect

    Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for silverstripe/cms, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.

  2. Fix

    A fix is available for CVE-2020-9311; check the affected-versions list above or the advisory for the patched release of silverstripe/cms, then make sure no transitive dependency still pins the vulnerable range.

  3. Workarounds

    Escape or sanitise the affected output on the server side rather than relying on client-side filtering, and add a Content-Security-Policy that blocks inline script execution so injected markup cannot run even if it reaches the page.

Frequently Asked Questions

In SilverStripe through 4.5, malicious users with a valid Silverstripe CMS login (usually CMS access) can craft profile information which can lead to XSS for other users through specially crafted login form URLs.
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CVE-2020-9311: cms XSS — Fixed in 3.7.5