LeafKit allows XSS with untrusted user input

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]