Complex sentence: It is possible for the entire system to be compromised by a malicious firmware, and without the ability to perform a security audit on manufacturer-provided firmware, even an innocent bug could undermine the safety of the running system.
Split into simpler sentences: It is possible for the entire system to be compromised by a malicious firmware, and without the ability to perform a security audit on manufacturer-provided firmware. Even an innocent bug could undermine the safety of the running system.