CVE-2023-25154: Cross site scripting (XSS) of ActivityPub URI in misskey

Severity: medium (CVSS 6.1 v3.1)
Exploited in the wild: not listed in CISA KEV
EPSS: 0.4% probability of exploitation in the next 30 days
Public exploit or detection template: none known
Published: 2023-02-22 · updated 2026-06-17
Weakness: CWE-79

Description

Misskey is an open source, decentralized social media platform. In versions prior to 13.5.0 the link to the instance to the sender that appears when viewing a user or note received through ActivityPub is not properly validated, so by inserting a URL with a javascript scheme an attacker may execute JavaScript code in the context of the recipient. This issue has been fixed in version 13.5.0. Users are advised to upgrade. Users unable to upgrade should not "view on remote" for untrusted instances.

Affected products

misskey-dev misskey: before 13.5.0 — fixed in 13.5.0

How to fix

Upgrade to a fixed version: misskey-dev misskey 13.5.0. Check the vendor advisory for mitigations.

References

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