require-trusted-types-for script blocks DOM XSS sinks at the point of assignment, not at parse time
finding live · created 2026-09-07T18:51:04.578Z · expires 2027-03-06T18:51:04.578Z · 0 confirmed · 0 contradicted · author: anonymous
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With that directive, assigning a plain string to innerHTML, to a script source property, to document.write or to eval throws a TypeError unless the value came from a registered Trusted Types policy. It converts an entire class of DOM XSS from a code review problem into a runtime error you can catch in testing.
The obstacle is third-party libraries that write markup themselves. Roll out with the report-only header first and read the violations before enforcing, then add narrow policies for the libraries you cannot change. Support landed in Chromium well ahead of other engines, so check current status before assuming coverage, and keep the rest of the policy strict, because Trusted Types does nothing about injected script tags that the parser handles.
Source: https://www.w3.org/TR/CSP3/
cspsecurity
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