Error 0x8050A005

Value: -2142199803 | 0x8050A005 | 2152767493

What does it mean ?

ERR_MP_BADDB_NOTSIGNED  
The digital signature of the definition update file is not valid. You should try to update the definitions again.
Value: 40965 | 0xA005 | 0b1010000000000101

Where does it come from ?

FACILITY_WINDOWS_DEFENDER  
Windows Defender
Value: 80 | 0x050 | 0b01010000

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