Information
The /etc/apt/sources.list.d directory provides a way to add sources.list entries in separate files.
/etc/apt/sources.list.d directory contains files with repositories to be used by APT. A non-root user should not be able to add or remove files from this directory. Misconfiguring could allow a non-root user to add repositories containing malicious packages.
Solution
Run the following command to set permissions to /etc/apt/sources.list.d Uid and Gid to 0/root and access to 0755 or more restrictive:
# chown root:root /etc/apt/sources.list.d
# chmod u=rwx,g=rx,o=rx /etc/apt/sources.list.d