Go html/template escaper bypass leads to XSS in <script> blocks
CVE-2026-39826 is a cross-site scripting vulnerability in Go's html/template package. When a trusted template author writes a <script> tag with an empty type attribute or a type attribute containing ASCII whitespace, the template engine incorrectly escapes data interpolated into that script block. This results in an escaper bypass in a context that should be treated as script content, allowing attacker-controlled data passed into the template to be emitted with insufficient escaping. The issue affects html/template's contextual auto-escaping logic for script tags under these malformed or ambiguous type-attribute conditions.
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