Sensitive data disclosure via nested CSS rule bypass
Published Apr 30, 2024 · Updated Mar 28, 2025
Information disclosure in CSS Exfil Protection 1.1.0 allows remote attackers to read sensitive page data through crafted nested CSS rules. The parseCSSRules function rejects wrapper rules lacking selectorText and does not recursively inspect their child CSSStyleRule objects, leaving exfiltration selectors unsanitized. Exploitation requires attacker-controlled CSS to render in a protected browser, where matching page values can trigger outbound requests to an attacker endpoint.
Summary
What happened
Information disclosure in CSS Exfil Protection 1.1.0 allows remote attackers to read sensitive page data through crafted nested CSS rules. The parseCSSRules function rejects wrapper rules lacking selectorText and does not recursively inspect their child CSSStyleRule objects, leaving exfiltration selectors unsanitized. Exploitation requires attacker-controlled CSS to render in a protected browser, where matching page values can trigger outbound requests to an attacker endpoint.
The record
- CVE
- CVE-2024-33437
- Published
- Apr 30, 2024
- Updated
- Mar 28, 2025
- Vendor
- Mike Gualtieri
- Product
- CSS Exfil Protection
- Classifications
- CWE-200, T1056
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Apr 30, 2024CVE publishedPublication date reported by the CVE source.
- Mar 28, 2025Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
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Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=1.1.0
What conditions does exploitation require?
What is affected?
Published CVSS scores
CVSS describes severity. EPSS estimates exploitation probability.
Attacks
What attackers are doing with it
Daily unique IPs observed by Shadowserver honeypots for known exploited vulnerabilities (KEVs). Missing observations do not establish an absence of attacks.
Weakness, pattern, technique
Public exploit references
- CSS Exfil Protection POCproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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