I feel that the word "backdoor" is incorrectly used here. ZTE confirmed a vulnerability discovered in the phone, not something they placed in the phone intentionally (backdoor).
Is that this: <a href="http://news.ycombinator.com/item?id=3994054" rel="nofollow">http://news.ycombinator.com/item?id=3994054</a><p>Because yeah, this has been known for a while...
Let's just say that, generally speaking, Russian and Chinese companies work very differently from those in USA. If their "CIA" shows up and wants something added, you either add it or you may be out of business...and that's if they're feeling generous. You can't exactly file a whistle blower lawsuit or go public with the info.