title: Cross site scripting (XSS) of ActivityPub URI in misskey
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.
problem types: CWE-79: Improper Neutralization of Input During Web Page Generation ('Cross-site Scripting')
affected:
{
vendor: misskey-dev
product: misskey
versions:
version: < 13.5.0, status: affected
}
metrics:
cvssV3_1: [
attackComplexity: LOW
attackVector: NETWORK
availabilityImpact: LOW
baseScore: 7.1
baseSeverity: HIGH
confidentialityImpact: LOW
integrityImpact: LOW
privilegesRequired: NONE
scope: CHANGED
userInteraction: REQUIRED
vectorString: CVSS:3.1/AV:N/AC:L/PR:N/UI:R/S:C/C:L/I:L/A:L
version: 3.1
]