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Thanks, Sushubh! That's exactly the reason, and I couldn't have said it better myself.
If the images load in Chrome and Opera, but not in Firefox, then it has something to do with your Firefox installation, and is specific to your computer. There's no way for me to know exactly what the problem is. Try disabling all extensions or running FF in safe mode. You also might want to try submitting a FF bug report.
It clearly states in Imgur's Terms of Service: "Hotlinking to file-sharing, torrent, and pornographic sites is prohibited." We're usually very lenient on this sort of thing, but it turned out that passthepopcorn was also using an incredible amount of bandwidth and resources. (The ToS also states: "keep in mind that this is a free service, so please be nice to our servers.")

Since it was violating the ToS, and it wasn't even nice about it, we decided to block it. I hope you understand.

The complete ToS is located here:
It's powered by Reddit. It will show other images from the same subreddit that the image is in. So for example, if you got there by clicking on an image in /r/fffffffuuuuuuuuuuuu, then it will display other images in /r/fffffffuuuuuuuuuuuu.
Thanks for letting me know about that. It's been fixed!
Hyperdesktop is not infected with a trojan. It's safe to say that your anti-virus is giving you a false positive.

This is my scan report:
There are two buttons -- "Done" and "Upload. "Done" is in the bottom left and "Upload" is in the bottom right. You don't need to paste the link for them to appear, so I'm not sure why you're not seeing them...
This never changed. The quality slider is still available, you just need to select "Edit" before you upload. Or, if you're in your account, select "Edit Images".

Sometimes the images are compressed if they are above 1MB in size, but again, the compression settings have not changed in over a year.
Imgur already does this, and has for some time. Here's the blog post that talks about it: