The best way to mitigate the ability of attackers or penetration testers to execute arbitrary payloads is to enforce application controls with allow lists (B). Application allow listing ensures that only pre-approved, trusted software and scripts can be executed on the system. This prevents attackers from dropping or running malicious binaries, even if they exploit vulnerabilities to gain access. CAS-005 emphasizes allow listing as a preventive control against post-exploitation persistence and lateral movement.

Option A (ASLR) randomizes memory addresses and helps mitigate buffer overflow exploits but does not directly prevent execution of unauthorized programs. Option C (OS restrictions of globally writable folders) improves security hygiene but still does not stop attackers from executing already placed payloads in non-restricted locations. Option D (EDR signatures) are reactive and limited, since attackers often use novel or obfuscated payloads not yet captured by signature databases.

Therefore, implementing application controls with allow lists provides the strongest defense against unauthorized payload execution in this context.