The Snowden leak showed that Cisco routers had been altered to enable surveillance [1]. Whether or not the manufacturer is complicit, or how the alteration is performed is ultimately irrelevant to the end user. Ultimately, the only people that got in legal trouble for this were Snowden and people who provided service to him.
[1]: https://arstechnica.com/tech-policy/2014/05/photos-of-an-nsa...
Actually it's entirely relevant how, in the context of this conversation.
Here, we're discussing product as shipped, not product intercepted and modified. We're discussing if products are shipped secure or not.
The Snowden disclosures are important, but not relevant in this case.