Stored XSS via callable media attribute action
Published May 11, 2026 · Updated May 11, 2026
Stored XSS in Grav before 2.0.0-beta.2 allows remote authenticated users with page editing permissions to execute JavaScript in viewers' browsers. Markdown image query parameters become dynamically invoked media actions; attribute() stores attacker-controlled names that Parsedown emits into image HTML without filtering event handlers. A victim must render the editor-controlled page, where the payload runs in the site origin and can read same-origin data or act with the victim's privileges.
Summary
What happened
Stored XSS in Grav before 2.0.0-beta.2 allows remote authenticated users with page editing permissions to execute JavaScript in viewers' browsers. Markdown image query parameters become dynamically invoked media actions; attribute() stores attacker-controlled names that Parsedown emits into image HTML without filtering event handlers. A victim must render the editor-controlled page, where the payload runs in the site origin and can read same-origin data or act with the victim's privileges.
The record
- CVE
- CVE-2026-42841
- Published
- May 11, 2026
- Updated
- May 11, 2026
- Vendor
- Grav
- Product
- Grav
- Classifications
- CWE-79, T1203
- Attack vector
- network
- Privileges
- authenticated
Timeline
How it unfolded
- May 11, 2026CVE publishedPublication date reported by the CVE source.
- May 11, 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=< 2.0.0-beta.2
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
- Markdown media attribute stored-XSS proof of conceptproof of concept · demonstrated
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Technologies
Your stack
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Your stack
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