ARM just licenses the ISA and provides some reference designs. Individual manufacturers can (and often do) add their own extensions and design the actual chips.

And peripherals that have direct CPU and memory access. You could easily design a “backdoor peripheral” to a completely bulletproof CPU.

Or other elements of an SoC. Biased RNG would be a good bet.

> Ok the claim is the CPU was compromised and they using ARM based tech.

MIPS and ARM.

And Linux MIPS doesn't even have DEP and ASLR.