Outline up to 1.4.x API Endpoint information disclosure

Summaryinfo

A vulnerability was found in Outline up to 1.4.x and classified as problematic. This vulnerability affects unknown code of the component API Endpoint. Executing a manipulation can lead to information disclosure. This vulnerability is handled as CVE-2026-28506. The attack can be executed remotely. There is not any exploit available. It is suggested to upgrade the affected component.

Detailsinfo

A vulnerability was found in Outline up to 1.4.x. It has been declared as problematic. This vulnerability affects an unknown code of the component API Endpoint. The manipulation with an unknown input leads to a information disclosure vulnerability. The CWE definition for the vulnerability is CWE-200. The product exposes sensitive information to an actor that is not explicitly authorized to have access to that information. As an impact it is known to affect confidentiality. CVE summarizes:

Outline is a service that allows for collaborative documentation. Prior to 1.5.0, the events.list API endpoint, used for retrieving activity logs, contains a logic flaw in its filtering mechanism. It allows any authenticated user to retrieve activity events associated with documents that have no collection (e.g., Private Drafts, Deleted Documents), regardless of the user's actual permissions on those documents. While the document content is not directly exposed, this vulnerability leaks sensitive metadata (such as Document IDs, user activity timestamps, and in some specific cases like the Document Title of Permanent Delete). Crucially, leaking valid Document IDs of deleted drafts removes the protection of UUID randomness, making High-severity IDOR attacks (such as the one identified in documents.restore) trivially exploitable by lowering the attack complexity. Version 1.5.0 fixes the issue.

The advisory is shared for download at github.com. This vulnerability was named CVE-2026-28506 since 02/27/2026. The exploitation appears to be easy. The attack can be initiated remotely. There are neither technical details nor an exploit publicly available. The MITRE ATT&CK project declares the attack technique as T1592.

Upgrading to version 1.5.0 eliminates this vulnerability.

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Productinfo

Name

• Outline

Version

• 1.0
• 1.1
• 1.2
• 1.3
• 1.4

Website

• Product: https://github.com/outline/outline/

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