CiviMail tracked links in WordPress site are marked down by Mail Tester
This is a known issue with all scripts in CiviCRM's extern directory - pointing directly to a PHP script inside wp-content is considered highly likely to be malicious. This will be solved out-of-the-box once the CiviCRM WP REST API Wrapper is merged into the CiviCRM WordPress plugin, but for now you probably need to install that and follow the instructions for replacing calls to those CiviCRM scripts with proper WordPress REST API calls.