CVE-2021-3783 is a medium-severity (CVSS 6.1) Cross-site Scripting (XSS) vulnerability in yourls/yourls. The records list no fixed version yet; check the vendor advisory below and apply the mitigations in the meantime.
Cross-site Scripting in yourls
EPSS Exploitation Probability
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
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
yourls is vulnerable to Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting') in arbitrary path handling.
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 🐘Packagist | yourls/yourls | all versions | No fix |
Affected Products
yourlsyourlsDetection & 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.
Remediation status
The records we use list no patched version of yourls/yourls for CVE-2021-3783. Check the maintainer's advisory, and where your build allows, override or pin the dependency away from the vulnerable range.
Mitigate without a patch
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
Is CVE-2021-3783 in your dependencies?
Find it across Packagist, including transitive dependencies.