GHSA-rv3x-xq3r-8j9h — leaf-kit
GHSA-rv3x-xq3r-8j9h is a Cross-site Scripting (XSS) vulnerability in github.com/vapor/leaf-kit. A fix is available for github.com/vapor/leaf-kit — see the affected versions and patch details below.
LeafKit allows XSS with untrusted user input
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.
Real-World Exposure
github.com/vapor/leaf-kitReal-time download stats are indexed for npm and PyPI packages. This vulnerability affects SwiftURL packages — download data is not available via public APIs for these ecosystems.
Description
Impact
This affects anyone passing unsanitised data to Leaf's variable tags. Before this fix, Leaf would not escape any strings passed to tags as variables. If an attacker managed to find a variable that was rendered with their unsanitised data, they could inject scripts into a generated Leaf page, which could enable XSS attacks if other mitigations such as a Content Security Policy were not enabled.
Patches
This has been patched in 1.3.0
Workarounds
Sanitise any untrusted input before passing it to Leaf and enable a CSP to block inline script and CSS data.
References
https://github.com/vapor/leaf-kit-ghsa-rv3x-xq3r-8j9h/pull/1
For more information
If you have any questions or comments about this advisory:
- Open an issue in Leaf Kit
- Email us at [email protected]
Affected Packages
| Ecosystem | Package | Vulnerable range | Fix |
|---|---|---|---|
| 📦SwiftURL | github.com/vapor/leaf-kit | all versions | 1.3.0 |
Detection & mitigation playbook
Open-source dependencyDetect
Scan your dependency tree (package-lock.json, pnpm-lock.yaml, requirements.txt, go.sum, etc.) for github.com/vapor/leaf-kit, including transitive dependencies — a direct dependency you never call can still pull in a vulnerable version.
Fix
Update github.com/vapor/leaf-kit to 1.3.0 or later, then make sure no transitive (indirect) dependency still pins the vulnerable range — O3 confirms GHSA-rv3x-xq3r-8j9h 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 GHSA-rv3x-xq3r-8j9h can be triaged on real exposure rather than presence alone.
Tailored to GHSA-rv3x-xq3r-8j9h. Runtime protection reduces exposure until a permanent patch is applied and verified — it complements patching, it doesn't replace it.
Frequently Asked Questions
Is GHSA-rv3x-xq3r-8j9h in your dependencies?
O3 Security finds GHSA-rv3x-xq3r-8j9h across SwiftURL dependencies, including transitive ones, and its impact-aware SCA ranks findings by whether your code actually calls the vulnerable path.