EDIT:
RIP Oleksandr, you and your add-ons will be missed. :(
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I hope the developer is ok. Just to let him know that Download Manager (S3) is breaking virustotal.com. For some reason the addon doesn't let me upload files to the site and the site triggers the captcha. After solving the captcha, the cycle repeat. Try to upload -> captcha->try to upload-captcha. Turning the addon off fixes the problem.