Simple Spoiler 1.2 - 1.3 - Unauthenticated Arbitrary Shortcode Execution

The The Simple Spoiler plugin for WordPress is vulnerable to arbitrary shortcode execution in versions 1.2 to 1.3. This is due to the plugin adding the filter add_filter('comment_text', 'do_shortcode'); which will run all shortcodes in comments. This makes it possible for unauthenticated attackers to execute arbitrary shortcodes.