Make the site GDPR compliant
Although supposedly going extinct, third party cookies are still in use by, for example, many Wordpress (feature adding) plugins. Wordpress covers around 30% of the websites on the internet.
Make the site GDPR compliant with, for example for Wordpress, plugins like Complianz – GDPR/CCPA Cookie Consent or WordPress compliance with GDPR/ePR and CCPA. Both give a list of all third-party cookies, including the hidden ones, being transmitted by the site to visitors. **