Hi, I have experienced a worrying problem since a few days on Thunderbird client (Windows). I recently received anonymous emails on my ISP mailbox. The sender has been disguised with display name of some of my recent recipients, but the sender is not visible when I open the message. The mail subject is also taken up from these recent emails. Each of these emails contains one of my personal family photos! These suspicious messages are only visible on Thunderbird 128.2.0esr (64 bits) Windows and not on web mail in a browser nor on the mail client of my smartphone! Inspection of the message source in Thunderbird does not show the email header... but only the binary code of the image that has been included as an attachment. It appears these incoming messages were modified locally in Thunderbird because I can see the original and valid emails from the senders in a web browser or from my smartphone. I suspect a malware is corrupting some inbox messages in Thunderbird. Norton did not detect any malware on my PC. Malwarebytes has quarantined a few PUPs/MUPs. Only one of my mailboxes is affected by this problem. Is there any known vulnerability in Thunderbird similar to this report? How can I block this kind of alteration of incoming mail?