An MDM report shows that a user's company cell phone has unauthorized applications installed.

Comprehensive and Detailed In-Depth Explanation:

If an MDM (Mobile Device Management) solution detects unauthorized applications, it is likely that the user has rooted (Android) or jailbroken (iOS) the device to bypass security restrictions. Root access allows the user to install unauthorized applications that MDM policies would normally block.

B. Upgraded the OS – Incorrect. Upgrading the OS does not bypass security policies or allow unauthorized apps.

C. Installed a VPN – Incorrect. A VPN does not affect the MDM system or allow unauthorized apps.

D. Uninstalled the MDM software – Incorrect. If the MDM software was removed, the device would not still be reporting to the MDM server.