If cleaned by MBAM, then the Remove selected option actually sends it to the MBAM Quarantine (unless you deleted it from there).
If it is still in there it could be restored added to the avast chest (see #### below) and sent to the virus labs. Whilst this process sends it back to the original location, there would be a limited risk of it being there, exercise care not to execute the file.
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Send the sample/s to avast as a Undetected Malware:
Open the chest and right click in the Chest and select Add, navigate to where you have the sample and add it to the chest (see image). Once in the chest, right click on the file and select 'Submit to virus lab...' complete the form and submit, the file will be uploaded during the next update. Note: manually adding to the chest doesn't remove them from the original location, so they still have to be dealt with in that location.
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Once you have sent this to the chest, run MBAM again (right click on the file ans select scan with Malwarebytes) to send it back to the MBAM chest.
