Cross-site scripting via unescaped Markdown angle brackets
Published Aug 23, 2026 · Updated Aug 23, 2026
Cross-site scripting in JustHTML 1.11.0 and earlier allows remote attackers to inject raw HTML through Markdown conversion. The to_markdown() serializer escapes only selected Markdown metacharacters while preserving angle brackets in text nodes, so entity-decoded or raw-text content becomes executable HTML when rendered. Exploitation requires attacker-controlled input to pass through to_markdown() and then reach an HTML-capable Markdown renderer; the result can execute script in the rendering user's browser.
Summary
What happened
Cross-site scripting in JustHTML 1.11.0 and earlier allows remote attackers to inject raw HTML through Markdown conversion. The to_markdown() serializer escapes only selected Markdown metacharacters while preserving angle brackets in text nodes, so entity-decoded or raw-text content becomes executable HTML when rendered. Exploitation requires attacker-controlled input to pass through to_markdown() and then reach an HTML-capable Markdown renderer; the result can execute script in the rendering user's browser.
The record
- CVE
- CVE-2026-8445
- Published
- Aug 23, 2026
- Updated
- Aug 23, 2026
- Vendor
- Emil Stenström
- Product
- JustHTML
- Classifications
- CWE-79, T1059.007
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Aug 23, 2026CVE publishedPublication date reported by the CVE source.
- Aug 23, 2026Record 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=0 <1.12.0
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
- Upstream Markdown sanitizer-bypass proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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