馃悰 Block spaced !important in inline style sanitizer - #40536
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powerivq merged 3 commits intoAug 13, 2026
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Aug 12, 2026
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INVALID_INLINE_STYLE_REGEX is the only CSS-level check isValidAttr runs on an inline style attribute, and its !important token assumes no whitespace between the ! and important. CSS permits whitespace there and browsers honor color:red ! important as an important declaration, so an author or template value like color:blue ! important slips past the denylist and lands in the DOM after reaching the purifier through amp-mustache, amp-bind [style], or amp-list, letting it override AMP protective !important rules. Relax the token to !\s*important so the spaced and tabbed forms are caught while valid styles and the existing position rules stay unchanged.