ether Etherpad up to 3.3.0 List Attribute src/static/js/domline.ts result.appendSpan Home cross site scripting

Summaryinfo

A vulnerability has been found in ether Etherpad up to 3.3.0 and classified as problematic. Affected is the function result.appendSpan of the file src/static/js/domline.ts of the component List Attribute Handler. This manipulation of the argument Home causes cross site scripting. This vulnerability appears as CVE-2026-55085. The attack may be initiated remotely. There is no available exploit.

Detailsinfo

A vulnerability has been found in ether Etherpad up to 3.3.0 and classified as problematic. Affected by this vulnerability is the function result.appendSpan of the file src/static/js/domline.ts of the component List Attribute Handler. The manipulation of the argument start with an unknown input leads to a cross site scripting vulnerability. The CWE definition for the vulnerability is CWE-79. The product does not neutralize or incorrectly neutralizes user-controllable input before it is placed in output that is used as a web page that is served to other users. As an impact it is known to affect integrity. The summary by CVE is:

Etherpad is a real-time collaborative editor. Prior to 3.3.1, result.appendSpan in src/static/js/domline.ts interpolates the start attribute of a numbered list directly into an unquoted ol start attribute before assigning the generated markup to node.innerHTML. ImportEtherpad.setPadRaw in src/node/utils/ImportEtherpad.ts accepts attacker-controlled attribute-pool values from a crafted .etherpad import, including list:number1 and a malicious start value. Any user with write access to a pad can store markup that executes as cross-site scripting when another user opens the pad or /timeslider, including when an administrator views the pad. This issue is fixed in version 3.3.1.

It is possible to read the advisory at github.com. This vulnerability is known as CVE-2026-55085 since 06/16/2026. The exploitation appears to be easy. The attack can be launched remotely. It demands that the victim is doing some kind of user interaction. Technical details of the vulnerability are known, but there is no available exploit. The attack technique deployed by this issue is T1059.007 according to MITRE ATT&CK.

Upgrading to version 3.3.1 eliminates this vulnerability.

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Productinfo

Vendor

• ether

Name

• Etherpad

Version

• 3.0
• 3.1
• 3.2
• 3.3.0

Website

• Product: https://github.com/ether/etherpad/

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