Photospace Responsive <= 2.1.1 - Authenticated (Administrator+) Stored Cross-Site Scripting

The Photospace Responsive plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the ‘psres_button_size’ parameter in versions up to, and including, 2.1.1 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with administrator-level permissions and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page. This only affects multi-site installations and installations where unfiltered_html has been disabled.