Even if you did review it, a motivated attacker is not going to have an exfiltrate_user_data(). The xz backdoor exploit was incredibly sophisticated, and one key of the design was sneaking a "." into a single line of a build test script.

A cursory audit of primary dependencies has almost zero chance of catching anything but a brazen exploit.

Yeah. Realistically I think the best course of action is just assume you’re already using a library that can exfiltrate data.

This requires allowlisting egress traffic and possibly even architecting things to prevent any one library from seeing too many things. This approach can be a big pain though and can be difficult to do practically.