The MSMDownload tool and required decrypted stock OxygenOS firmware for OnePlus 8 and OnePlus 8 Pro was published by XDA OG Some_Random_Username on this and this XDA thread, respectively. The tool will automatically unlock the phone’s bootloader before flashing the firmware and relock it later after the unbricking process finishes. The best part about using this tool and this method is that it also works even if your phone has a locked bootloader. So, even if your phone’s secondary bootloader (the one that is normally responsible for booting the phone) is inaccessible, you can boot your OnePlus 8/8 Pro into EDL mode, connect it to your PC, and use the MSMDownload tool to unbrick the phone. This special boot-mode is a feature available only for devices equipped with Qualcomm SoCs and is controlled by the primary bootloader. MSMDownload Tool basically communicates with your phone over Qualcomm’s EDL mode ( Emergency Download Mode) to flash the stock OxygenOS firmware. However, the tool was leaked for almost every OnePlus device in the past and is now available for the OnePlus 8 and OnePlus 8 Pro as well, all thanks to some awesome members of the community. It is a low-level flashing utility that is used by OnePlus (and its parent company Oppo) to carry out flashing on their devices internally. Now, if you have found yourself in this ordeal, you can easily unbrick your OnePlus 8/8 Pro using the MSMDownload tool. Unbricking a Hard-bricked OnePlus 8/8 Pro And if you cannot boot into Fastboot/Recovery mode either, it means that you cannot install the stock firmware by flashing the Fastboot ROM or Recovery Mode to unbrick it easily. If your OnePlus 8/8 Pro ticks any of the signs listed above, then it’s probably hard-bricked. Your phone shows the Qualcomm CrashDump Mode screen and is identified as ‘ Qualcomm HS-USB Diagnostics 900E‘ in Device Manager when connected over USB.When connected to a Windows PC using a USB, the phone is detected as ‘ QUSB_BULK‘ or ‘ Qualcomm HS-USB QDLoader 9008‘ interface under Windows Device Manager.That’s because the secondary bootloader is inaccessible.
Your phone shows the ‘ Your Device is corrupt‘ message while booting and performing a factory reset doesn’t make any difference.