Information
The extension directory is the location of the PostgreSQL extensions. Extensions are storage engines or user defined functions (UDFs).
Limiting the accessibility of these objects will protect the confidentiality, integrity, and availability of the PostgreSQL database. If someone can modify extensions, then these extensions can be used to execute illicit instructions.
Solution
If needed, correct the permissions on the extension dir by executing:
sudo chown root:root $ext_dir
sudo chmod 0755 $ext_dir
If the permissions needed correct, it is imperative that all extensions found in $ext_dir are evaluated to ensure they have not been modified!