Until there is more information, no non-nexus cables in nexus chargers.
Here's a video explaining the issue:
https://www.youtube.com/watch?v=DMPrM0eWPbY
A summary is that the Nexus chargers (that come in the box with the phones) will supply power to anything connected to the other end, not only things that identify themselves as devices that need to be charged by that charger. This impacts almost all cables on the 5X and "smart" cables on the 6P. The 22.5W one that you can by from the google store here: https://forums.androidcentral.com/e.../store.google.com/us/?hl=en-US&token=hzncmqmh does not contain this issue.
I don't know if there are people that use third party cables with their OEM wall chargers, but if you do, don't do that with the Nexus 6P and 5X chargers.
Here's a video explaining the issue:
https://www.youtube.com/watch?v=DMPrM0eWPbY
A summary is that the Nexus chargers (that come in the box with the phones) will supply power to anything connected to the other end, not only things that identify themselves as devices that need to be charged by that charger. This impacts almost all cables on the 5X and "smart" cables on the 6P. The 22.5W one that you can by from the google store here: https://forums.androidcentral.com/e.../store.google.com/us/?hl=en-US&token=hzncmqmh does not contain this issue.
I don't know if there are people that use third party cables with their OEM wall chargers, but if you do, don't do that with the Nexus 6P and 5X chargers.