I downloaded an IPA file from http://m.qq.com/ , and install it to my jailbroken iPhone with iFunBox, run and after some self configurating, it rebooted automatically, and when the device restarted, a deb that was built in that IPA file was installed.
I knew that installing deb packages requires root privilege, but the internal executable in that IPA file is normal application, so it made me confused.
PS: SBSettings is not installed on my iPhone, so the answer cannot solve my problem.