The Post Views Stats Counter plugin for WordPress is vulnerable to Stored Cross-Site Scripting via User-Agent Header in all versions up to, and including, 1.1.7 due to insufficient input sanitization and output escaping. This makes it possible for unauthenticated attackers to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. The plugin's only input filter is a substring blacklist for known bot signatures (e.g. 'bot', 'spider', 'crawler'), which can be trivially bypassed by crafting a User-Agent payload that omits those strings.