Certain software builds for the TCL 30Z and TCL 10 Android devices contain a vulnerable, pre-installed app that relies on a missing permission that provides no protection at runtime. The missing permission is required as an access permission by components in various pre-installed apps. On the TCL 30Z device, the vulnerable app has a package name of com.tcl.screenrecorder (versionCode='1221092802', versionName='v5.2120.02.12008.1.T' ; versionCode='1221092805', versionName='v5.2120.02.12008.2.T'). On the TCL 10L device, the vulnerable app has a package name of com.tcl.sos (versionCode='2020102827', versionName='v3.2014.12.1012.B'). When a third-party app declares and requests the missing permission, it can interact with certain service components in the aforementioned apps (that execute with "system" privileges) to perform arbitrary files reads/writes in its context. An app exploiting this vulnerability only needs to declare and request the single missing permission and no user interaction is required beyond installing and running a third-party app. The software build fingerprints for each confirmed vulnerable device are as follows: TCL 10L (TCL/T770B/T1_LITE:11/RKQ1.210107.001/8BIC:user/release-keys) and TCL 30Z (TCL/4188R/Jetta_ATT:12/SP1A.210812.016/LV8E:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU5P:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU61:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU66:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU68:user/release-keys, TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU6P:user/release-keys, and TCL/T602DL/Jetta_TF:12/SP1A.210812.016/vU6X:user/release-keys). This malicious app declares the missing permission named com.tct.smart.switchphone.permission.SWITCH_DATA as a normal permission, requests the missing permission, and uses it to interact with the com.tct.smart.switchdata.DataService service component that is declared in vulnerable apps that execute with "system" privileges to perform arbitrary file reads/writes.

MITRE https://media.defcon.org/DEF%20CON%2031/DEF%20CON%2031%20presentations/Ryan%20Johnson%20Mohamed%20Elsabagh%20Angelos%20Stavrou%20-%20Still%20Vulnerable%20Out%20of%20the%20Box%20Revisiting%20the%20Security%20of%20Prepaid%20Android%20Carrier%20Devices.pdf [No types assigned]