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.
This has been patched in 1.3.0
Sanitise any untrusted input before passing it to Leaf and enable a CSP to block inline script and CSS data.
https://github.com/vapor/leaf-kit-ghsa-rv3x-xq3r-8j9h/pull/1
If you have any questions or comments about this advisory: * Open an issue in Leaf Kit * Email us at security@vapor.codes