I have written before about the Silent Circle Blackphone. (The articles are available at http://goo.gl/sjc8rc, http://goo.gl/ix8cfC, and at http://goo.gl/wqNSJq.) These cell phones give users complete control of app permissions and include encrypted services such as Silent Phone and Silent Text, designed to prevent surveillance and eavesdropping. However, no product is ever perfect and now researchers have recently discovered a flaw in the Blackphone system which could lead to modem tampering and call record surveillance.
The odds of being hacked are probably slim but certainly not zero. This is (or was) a serious vulnerability. Silent Circle has already patched the problem and issued a mass patch deployment on 7 December 2015. If you have installed the patch, the vulnerability has been fixed on your phone. However, if you have not yet installed the patch, you need to do so NOW.
Details may be found at http://goo.gl/I1JJWs.