The ZTE Score M is an Android 2.3.4 (Gingerbread) phone available in the United States on MetroPCS, made by Chinese telecom ZTE Corporation.
There is a setuid-root application at /system/bin/sync_agent that serves no function besides providing a root shell backdoor on the device. Just give the magic, hard-coded password to get a root shell:
$ sync_agent ztex1609523
Nice backdoor, ZTE.