Misskey Directory Traversal Vulnerability in AiScript via `Mk:api`

Misskey is an open source, federated social media platform. Starting in version 12.31.0 and prior to version 2025.4.1, missing validation in Mk:api allows malicious AiScript code to access additional endpoints that it isn't designed to have access to. The missing validation allows malicious AiScript code to prefix a URL with ../ to step out of the /api directory, thereby being able to make requests to other endpoints, such as /files, /url, and /proxy. Version 2025.4.1 fixes the issue.