Email Subscribers & Newsletters <= 5.9.10 - Missing Authentication to Unauthenticated Action Scheduler Task Execution

The Icegram Express - Email Subscribers, Newsletters and Marketing Automation Plugin for WordPress is vulnerable to Missing Authorization in versions up to, and including, 5.9.10. This is due to the plugin not properly verifying that a user is authorized to perform an action in the `run_action_scheduler_task` function. This makes it possible for unauthenticated attackers to execute scheduled actions early or repeatedly by guessing action IDs, potentially triggering email sends, maintenance tasks, or other privileged operations, causing unexpected state changes and resource usage.