CVE-2026-27120

The record

Leafkit is a templating language with Swift-inspired syntax. Prior to 1.4.1, htmlEscaped in leaf-kit will only escape html special characters if the extended grapheme clusters match, which allows bypassing escaping by using an extended grapheme cluster containing both the special html character and some additional characters. In the case of html attributes, this can lead to XSS if there is a leaf variable in the attribute that is user controlled. This vulnerability is fixed in 1.4.1.

Affected packages

Related vulnerabilities

• GHSA-4hfh-fch3-5q7p Leaf-kit html escaping does not work on characters that are part of extended grapheme… Same vulnerability
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• CVE-2026-96379 Improper Neutralization of Input During Web Page Generation ("Cross-site Scripting")… CWE-79
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