Summary
Missing validation in ApRequestService.signedGet and HttpRequestService.getActivityJson allows an attacker to create fake user profiles and forged notes. The spoofed users will appear to be from a different instance than the one where they actually exist, and the forged notes will appear to be posted by a different user.
Impact
Vulnerable Misskey instances will accept the spoofed objects as valid, allowing an attacker to impersonate other users and instances. The attacker retains full control of the spoofed user / note and can interact like a real account.
Summary
Missing validation in
ApRequestService.signedGetandHttpRequestService.getActivityJsonallows an attacker to create fake user profiles and forged notes. The spoofed users will appear to be from a different instance than the one where they actually exist, and the forged notes will appear to be posted by a different user.Impact
Vulnerable Misskey instances will accept the spoofed objects as valid, allowing an attacker to impersonate other users and instances. The attacker retains full control of the spoofed user / note and can interact like a real account.