CVE-2020-27388 is a medium-severity (CVSS 5.4) Cross-site Scripting (XSS) vulnerability in yourls/yourls. A fix is available for yourls/yourls — see the affected versions and patch details below.
YOURLS Stored Cross Site Scripting (XSS)
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-2020-27388 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 378,156 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
yourls/yourlsReal-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
Multiple Stored Cross Site Scripting (XSS) vulnerabilities exist in the YOURLS Admin Panel, Versions 1.5 - 1.7.10. An authenticated user must modify a PHP plugin with a malicious payload and upload it, resulting in multiple stored XSS issues.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | yourls/yourls | ≥ 1.5&&< 1.8 | 1.8composer require yourls/yourls:^1.8 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for yourls/yourls, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update yourls/yourls to 1.8 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms CVE-2020-27388 is resolved across your whole dependency graph.
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-2020-27388 can be triaged on real exposure rather than presence alone.
Tailored to CVE-2020-27388. 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-2020-27388 in your dependencies?
O3 Security finds CVE-2020-27388 across Packagist dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.