Serialize JavaScript: Cross-site scripting (XSS) via unescaped </script at the end of a serialized function body

Serialize JavaScript serializes JavaScript values to a superset of JSON that includes regular expressions and functions. Prior to 7.1.3, the function-source escaping logic does not neutralize a bare closing-script prefix when attacker-influenced function source text ends exactly at that prefix. Because each function body is escaped independently, a delimiter supplied by surrounding serialized output can terminate an HTML script element, and a later serialized value supplies injected markup that becomes a live element in the page. Exploitation requires control of a serialized function's source text, such as through a spoofed toString(). This issue is fixed in version 7.1.3.

Source published

23 Oct 2026 21:37:41 UTC

Source modified

23 Oct 2026 21:37:41 UTC

Observed here

23 Oct 2026 22:48:20 UTC

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CVSS 4.0 · 2.1 CVSS:4.0/AV:N/AC:H/AT:P/PR:L/UI:P/VC:L/VI:L/VA:N/SC:L/SI:L/SA:N