Artalk before 2.10.1 Unauthenticated SSRF via Comment Page Title Fetch

Artalk before 2.10.1 contains an unauthenticated server-side request forgery vulnerability that allows remote attackers to make the server fetch arbitrary URLs by submitting anonymous comments to /api/v2/comments. Attackers can set a page_key to an internal URL, which GetTitleByURL fetches after only scheme validation, then read the page title through the public comment list.