Is CVE-2026-43887 exploited in the wild?

No. Junglewise Threat Intelligence has no report of CVE-2026-43887 being exploited in the wild.

How severe is CVE-2026-43887?

High severity, with a CVSS score of 7.3, published 11 May 2026.

Which products and versions are affected?

Outline Outline 0.84.0 to 1.6.1.

Is there a fix for CVE-2026-43887?

A patch was published on 2026-05-11: Fix confirmed available in version 1.7.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.

How is CVE-2026-43887 attacked?

It is attacked over the network, in a web application.

Am I affected by CVE-2026-43887?

Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

CVE-2026-43887: Outline stored XSS in comment mentions

CVE-2026-43887 · Severity: high · CVSS 7.3 · Published 2026-05-11

Outline is a collaborative documentation platform used by teams to share and manage knowledge. A security flaw in the platform's comment section allows users to embed malicious links that, when clicked by another user, can execute unauthorized code in their browser. This could lead to the theft of sensitive session information, unauthorized access to private documents, or the compromise of user accounts within the wiki.

Quick answers

Is CVE-2026-43887 exploited in the wild?: No. Junglewise Threat Intelligence has no report of CVE-2026-43887 being exploited in the wild.
How severe is CVE-2026-43887?: High severity, with a CVSS score of 7.3, published 11 May 2026.
Which products and versions are affected?: Outline Outline 0.84.0 to 1.6.1.
Is there a fix for CVE-2026-43887?: A patch was published on 2026-05-11: Fix confirmed available in version 1.7.0 Junglewise finds every place you run it, drafts the upgrade and applies it once you approve.
How is CVE-2026-43887 attacked?: It is attacked over the network, in a web application.
Am I affected by CVE-2026-43887?: Check whether anything you run is named in the advisory. Junglewise does that check for you around the clock: connect your code, cloud and domains, and it matches new vulnerabilities like this one against what you actually run and tells you when one reaches you.

Technical details

A stored cross-site scripting (XSS) vulnerability exists in Outline versions 0.84.0 through 1.6.1 due to improper input validation in the comment mention system. The backend fails to sanitize the 'href' attribute for certain mention types (Issue, PullRequest, Project, and URL) within the 'toDOM' function of the Mention node component. An authenticated attacker can bypass the standard UI by sending a crafted API request to '/api/comments.create' containing a 'javascript:' URI. When another user clicks the resulting mention link, the malicious script executes in their browser context. While Content Security Policy (CSP) may mitigate some exploitation, the underlying flaw allows for session hijacking and data exfiltration. The issue is resolved in version 1.7.0 by implementing the 'sanitizeUrl' function.

Affected products

Outline Outline 0.84.0 to 1.6.1

Timeline

2026-04-25: advisory: GitHub security advisory published by maintainers
2026-05-11: disclosed: CVE published to NVD
2026-05-11: patched: Fix confirmed available in version 1.7.0

References

https://github.com/outline/outline/security/advisories/GHSA-rqrg-f3qc-xvgh

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