Google XML Sitemap for Images <= 2.1.3 is vulnerable to Cross Site Request Forgery (CSRF) vulnerability

The Google XML Sitemap for Images plugin for WordPress is vulnerable to Cross-Site Request Forgery in versions up to, and including, 2.1.3. This is due to missing or incorrect nonce validation on the image_sitemap_generate() function. This makes it possible for unauthenticated attackers to generate image sitemaps via a forged request granted they can trick a site administrator into performing an action such as clicking on a link.