Input validation vulnerability in Coupon API 6.2.9

The Coupon API plugin for WordPress has a security issue called SQL Injection. This happens when someone uses a specific part of the plugin called ‘log_duration’ in a harmful way. This can happen in all versions up to 6.2.9. The problem is caused by not properly protecting the ‘log_duration’ part and not preparing the database well enough. This means that someone who has a high level of access, like an Administrator, can add more harmful code to the already existing code and get information from the database that should be kept private.