I use an antivirus software called Malwarebytes on top of the normal antivirus software (Bitdefender Total Security) to detect viruses and malwares not detected by Bitdefender Total Security. Bitdefender does not detect the trojan in the images but Malwarebyte does. There could be viruses and malwares that Malwarebyte may not detect.

Most people use the normal commercial softwares like Avast, Bitdefender etc and therefore wouldn't have detected it. Additionally, because you are just starting off, your readership is not big and neither the userbase of steem-engine.com and so not many people would have detected it and some even if aware of it, may not have bothered to complain. Rest assured as your readership increases, you will get more complaints.

Steem-engine is aware of the problem because I told them so and they are going to address it.

I suggest you stop using images from imagesafe. This would be a proactive and prudent step from your end. Of course you are free to continue using it also. That is your prerogative.