Session-token theft via unsanitized LLM chat output
Published Jul 22, 2025 · Updated Jul 22, 2025
Stored XSS in Chaindesk through 2025-05-26 allows remote attackers to execute JavaScript in a victim's browser via agent chat. The agent chat renderer treats LLM-generated SVG and script markup induced by an attacker-controlled system prompt as executable page content instead of neutralizing it. A victim must interact with the malicious agent or open its conversation link; the resulting script can read JWT session tokens and enable account hijacking.
Summary
What happened
Stored XSS in Chaindesk through 2025-05-26 allows remote attackers to execute JavaScript in a victim's browser via agent chat. The agent chat renderer treats LLM-generated SVG and script markup induced by an attacker-controlled system prompt as executable page content instead of neutralizing it. A victim must interact with the malicious agent or open its conversation link; the resulting script can read JWT session tokens and enable account hijacking.
The record
- CVE
- CVE-2025-51859
- Published
- Jul 22, 2025
- Updated
- Jul 22, 2025
- Vendor
- Unknown vendor
- Product
- Unknown product
- Classifications
- CWE-79, T1189
- Attack vector
- network
- Privileges
- unauthenticated
Timeline
How it unfolded
- Jul 22, 2025CVE publishedPublication date reported by the CVE source.
- Jul 22, 2025Record 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?
What conditions does exploitation require?
What is affected?
Affected products and versions are unavailable in this record.
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
- CVE-2025-51859 Chaindesk stored-XSS proof of conceptproof 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