The Easy Image Gallery plugin for WordPress is vulnerable to Stored Cross-Site Scripting via the Gallery shortcode post meta field in all versions up to, and including, 1.5.3. This is due to insufficient input sanitization and output escaping on user-supplied gallery shortcode values. 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.
CWE-79