CVE-2020-9311 — silverstripe/cms
MEDIUMCVE-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
EPSS Exploitation Probability
EPSS (Exploit Prediction Scoring System) is a daily probability model maintained by FIRST.org. It estimates the likelihood a CVE will be exploited in production environments within the next 30 days, derived from real-world threat intelligence signals.
How urgent is this, really
CVE-2020-9311 plotted by exploitation likelihood (EPSS) against impact (CVSS). The shaded corner — EPSS 50%+ and CVSS 7.0+ — is where this CVE doesn't sit, though severity or exploitability alone can still warrant action.
Where this sits among everything scored
Of 377,636 CVEs with a current EPSS score, this one falls in the < 10% band (highlighted). Real counts from FIRST.org, not a sample — log-scaled since the landscape is heavily right-skewed.
Real-World Exposure
silverstripe/cms🐘silverstripe/frameworkReal-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
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | silverstripe/cms | all versions | No fix |
| 🐘Packagist | silverstripe/framework | ≥ 3.0.0&&< 3.7.5 | 3.7.5composer require silverstripe/framework:^3.7.5 |
Detection & mitigation playbook
Open-source dependencyDetect
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.
Fix
No patched version of silverstripe/cms has shipped for CVE-2020-9311 yet. Where your build allows, override or pin the dependency away from the vulnerable range, and apply any maintainer-recommended mitigation.
Workarounds
If you can't upgrade right away: gate or disable the affected feature, validate untrusted input at the boundary, and avoid passing attacker-controlled data into the vulnerable path. O3's runtime protection blocks exploitation in production as an interim safeguard until the upgrade lands.
How O3 protects you
O3 Security's impact-aware SCA analyses which vulnerable code paths your application actually calls, so a match like CVE-2020-9311 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2020-9311. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is CVE-2020-9311 in your dependencies?
O3 Security finds CVE-2020-9311 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.