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OpenAdvisories
Medium · 6.1 CVE-2026-27120 EUVD-2026-7783GHSA-4hfh-fch3-5q7p

Leaf-kit html escaping does not work on characters that are part of extended grapheme cluster

Published Feb 20, 2026 · Updated Feb 24, 2026 · Assigned by GitHub_M

Description

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 products

VendorProductAffectedFixed
vapor leaf-kit < 1.4.1 —

Affected packages

EcosystemPackageAffectedFixedRecord
SwiftURL github.com/vapor/leaf-kit < 1.4.1 1.4.1 GHSA-4hfh-fch3-5q7p

References