Incorrect escaping for `url("")` functions in CSS style attributes

CISA KEV is observed exploitation evidence. FIRST EPSS is a dated prediction of exploitation in the next 30 days. Missing scores are unknown. This collector requests predictions only for explicit CVE aliases in the public NuGet archive; Microsoft release views retain their existing prediction scope.

No collected risk observation for these identifiers. This does not establish absence of exploitation or a zero probability.

In some cases, quotation marks in CSS url() functions are not escaped. This allows CSS injection. This feature is not enabled by default, so an application is vulnerable if, and only if, the style attribute is allowed and filter_style_properties is used. As an example, this snippet: ```html <div style='background:url("cid:\");EVIL_CSS_HERE;background:url(\"cid:")'> ``` Would erroneously "sanitize" to: ```html <div style='background:url("cid:");EVIL_CSS_HERE;background:url("cid:")'> ``` --- This vulnerability was reported by Uttej Badwane

Source published

10 Oct 2021 12:00:00 UTC

Source modified

12 Oct 2026 18:15:01 UTC

Observed here

24 Oct 2026 13:19:54 UTC

Source terms

OSV · upstream source license applies

Original source record · Cite this exact observation · Complete original publisher JSON

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