Mutation XSS via unescaped RCDATA in foreign content
Published Mar 24, 2020 · Updated Aug 4, 2024
Mutation XSS in Mozilla Bleach 3.1.1 and earlier allows remote attackers to execute JavaScript through crafted sanitized HTML. BleachHTMLSerializer leaves RCDATA characters unescaped when bleach.clean processes whitelisted svg or math and RCDATA elements with strip=False, so browser reparsing lifts a malicious element into executable HTML. Exploitation requires that nondefault allowlist combination, attacker-controlled input, and a user who renders the sanitized output; it enables script execution in the application's origin.
Summary
What happened
Mutation XSS in Mozilla Bleach 3.1.1 and earlier allows remote attackers to execute JavaScript through crafted sanitized HTML. BleachHTMLSerializer leaves RCDATA characters unescaped when bleach.clean processes whitelisted svg or math and RCDATA elements with strip=False, so browser reparsing lifts a malicious element into executable HTML. Exploitation requires that nondefault allowlist combination, attacker-controlled input, and a user who renders the sanitized output; it enables script execution in the application's origin.
The record
- CVE
- CVE-2020-6816
- Published
- Mar 24, 2020
- Updated
- Aug 4, 2024
- Vendor
- Mozilla
- Product
- Bleach
- Classifications
- CWE-79, CAPEC-63, T1059.007
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Mar 24, 2020CVE publishedPublication date reported by the CVE source.
- Aug 4, 2024Record updatedLatest update available in the CVE record.
Exploitability
Present is not the same as exploitable
Compare your product and version with the public record. A matching version still requires validation against your environment.
Is a vulnerable build present?
Compare these published version ranges with your installed build and any vendor patches.
- Affected versionversion=<=3.11
What conditions does exploitation require?
What is affected?
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
- Checkmarx bleach.clean mutation-XSS reproductionproof of concept · demonstrated
Labels summarize the accepted research assessment. They do not indicate a test against your environment.
Technologies
Your stack
See the directory against your own environment.
Your stack
Check the software in your environment
Book a demo to see how Hinoki identifies affected software and validates exploitability in your environment.
Book a demo