Yes, but it's not hidden, people are aware that it's a threat. And these things do get checked at least, people fuzzing opcodes to expose hidden functionality. It's still generally a terrible idea, but it's not yet "backdoor in a box" like the (so far unfounded as I undestand) allegations against Huawei. Still, if I'm Cisco, I don't run my Wifi off of Huawei access points.
If you're Cisco you might not run a 1:1 competitor's products, but they do use Huawei hardware, i.e. LTE equipment.
Same goes for things like mobile phone manufacturers, they are competing with Samsung, but they will still buy Samsung LCDs for their own phones.
Samsung is a SoC manufacturer, but they will happily buy a SoC from Qualcomm. Same with DRAM, they make that too, but having Micron DRAM doesn't scare them either.
And the circle back to Cisco: they happily use Broadcom switch chips in their Cisco switches.
