YesWiki is a wiki system written in PHP. From version 4.2.0 to before version 4.6.6, ApiController::deletePage() interpolates a page tag retrieved from the database into a DELETE FROM …_links WHERE to_tag = '$tag' query without escaping. The page tag is attacker-controlled — the POST /api/pages/{tag} API accepts arbitrary URL-encoded values, including single quotes, and stores them. A low-privilege authenticated user can therefore create a page whose tag is a SQL fragment, make the page non-orphaned via the standard {{include page="…"}} link mechanism, and then invoke the delete endpoint to execute arbitrary SQL inside the wiki database - including time-based blind data exfiltration from any table. This issue has been patched in version 4.6.6.