Hi @Anonym0us
You can check whether the prompt came from Microsoft Defender by opening Windows Security > Virus & threat protection > Protection history. Expand entries from the time of the Brave update and check whether the file name, path, and action match what you saw. Administrator permission may be required, and Protection History retains events for only two weeks.
Microsoft Defender may request permission to send a file sample when cloud protection cannot determine whether it is safe. Under the default setting, safe samples are submitted automatically, but Windows asks permission when a file might contain personal information.
You can also open Windows Security > Virus & threat protection > Manage settings and review Cloud-delivered protection and Automatic sample submission. A different prompt on the two PCs is not necessarily suspicious because Defender may have needed additional analysis only on one device.
Windows does not normally provide a user-facing report showing the final cloud-analysis result for every submitted sample. If Protection History shows no threat and a current scan is clean, no additional action is normally required. You may run a Quick scan for reassurance.
See Protection History in the Windows Security App for more details: Protection History in the Windows Security App.
I hope this helps, please feel free to let me know if you need any further help.