Stored XSS via unsafe Markdown autolinks
Published Feb 8, 2023 · Updated Mar 25, 2025
Stored XSS in Apache Answer before 1.0.4 allows remote authenticated users to execute JavaScript when another user views a crafted post. The DangerousHTMLRenderer omitted a handler for Markdown autolinks, so attacker-controlled autolink URLs and labels bypassed its URL validation and HTML escaping. A low-privileged account must store the payload and a second user must view the rendered content, allowing script execution in that user's browser context.
Summary
What happened
Stored XSS in Apache Answer before 1.0.4 allows remote authenticated users to execute JavaScript when another user views a crafted post. The DangerousHTMLRenderer omitted a handler for Markdown autolinks, so attacker-controlled autolink URLs and labels bypassed its URL validation and HTML escaping. A low-privileged account must store the payload and a second user must view the rendered content, allowing script execution in that user's browser context.
The record
- CVE
- CVE-2023-0740
- Published
- Feb 8, 2023
- Updated
- Mar 25, 2025
- Vendor
- The Apache Software Foundation
- Product
- Apache Answer
- Classifications
- CWE-79, T1059.007
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- Feb 8, 2023CVE publishedPublication date reported by the CVE source.
- Mar 25, 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?
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- Affected versionversion=unspecified <1.0.4
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
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Technologies
Your stack
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Your stack
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