Magazine Blocks < 1.3.21 - Authenticated (Contributor+) Stored Cross-Site Scripting

Description

The Magazine Blocks plugin for WordPress is vulnerable to Stored Cross-Site Scripting in versions up to, and including, 1.3.20 due to insufficient input sanitization and output escaping. This makes it possible for authenticated attackers, with contributor-level access and above, to inject arbitrary web scripts in pages that will execute whenever a user accesses an injected page.