Protector -> Legacy XoopsDB is deprecated since 2.6.0
In debugbar: Legacy XoopsDB is deprecated since 2.6.0; all calls should be using Doctrine through $xoops->db(). Called from query() in ROOT/modules/protector/admin/index.php line 30
Protector needs to be refactored, and is on the radar. I've been holding off until a couple of other things that will also require changes are implemented. It will continue to need to use legacy hooks to protect legacy code, which will also trigger deprecation warnings. The new DBAL based access uses bound parameters, and take prevents many of the SQL based attacks that Protector has traditionally prevented.
Only one deprecated message will be generated per run, but it will nag us by design.