Serialize JavaScript: Cross-site scripting (XSS) via unescaped </script> in serialized function bodies

Serialize JavaScript serializes JavaScript values to a superset of JSON that includes regular expressions and functions. From 7.1.1 until 7.1.2, function values serialized by serialize-javascript are not fully protected against script-closing tags in attacker-influenced function source because SCRIPT_CLOSE_REGEXP can consume a second closing tag inside one match. When the serialized function is embedded in a script element, the surviving closing tag terminates the element early and causes the remaining output to be parsed as HTML, enabling cross-site scripting in the page origin. Only function values are affected; ordinary data values and options.isJSON output are unaffected. This issue is fixed in version 7.1.2.

Source published

29 Sep 2026 16:00:33 UTC

Source modified

29 Sep 2026 16:53:35 UTC

Observed here

23 Oct 2026 15:48:27 UTC

Source terms

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CVSS 4.0 · 2.3 CVSS:4.0/AV:N/AC:L/AT:P/PR:N/UI:P/VC:N/VI:N/VA:N/SC:L/SI:L/SA:N