Path-relative style sheet import
Summary: PortSwigger Research describes path-relative style sheet import vulnerabilities, which arise under specific conditions and let an attacker construct a URL that causes the victim's browser to import a different URL as CSS, containing text the attacker can manipulate. The result is arbitrary CSS injection in the victim's browser, which may enable various attacks, and the root cause is resolved by not using path-relative URLs in style sheet imports.
Key Takeaway: The fix is a single change - stop using path-relative URLs in style sheet imports - yet the payoff for an attacker is arbitrary CSS injection inside your users' browsers, and PortSwigger notes this issue and many like it are found by its scanner.
Read the original at PortSwigger Research ↗
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