AIKIDO-2026-10703

TL;DR

The JSX runtime exposed programmatic element creation through jsx() and createElement() while emitting opening tags using raw tag names from callers. Attribute names and values were hardened elsewhere, but tag names themselves were not constrained, so values containing markup-breaking characters could reshape the generated HTML string when tag strings originate from untrusted sources. The corrected implementation rejects unsafe tag names before serialization so output stays within the intended element boundary and cannot introduce sibling markup or attributes through the tag token.