The Strapi Protected Populate Plugin protects `get` endpoints from revealing too much information. Prior to version 1.3.4, users were able to bypass the field level security. Users who tried to populate something that they didn't have access to could populate those fields anyway. This issue has been patched in version 1.3.4. There are no known workarounds.
https://github.com/strapi-community/strapi-plugin-protected-populate/releases/tag/v1.3.4