On login to my bank, Firefox has a popup asking me to open or download a file called ibank.dll. This happens only on this browser, not on Explorer, Opera, or Safari.
When logging in on my bank, Firefox also loads a box with "You have chosen to open ibank.dll which is a document from https://[bank name site]. I can still log into my account, but the extra window is annoying. This happens only on Firefox. It does not occur if I log in from Explorer, Opera, or Safari. I use an iMac.
URL of affected sites
Clearing the cache and/or deleting cookies does not affect this problem. Checking or unchecking allow popups does not affect the problem, either.
This occurs only on Firefox.
Clearing cache and/or erasing cookies does not solve the issue.
Clearing cache and/or deleting cookies does not resolve this issue. This happens only on Firefox.
According to this, it is a problem with the bank site's software:
According to this, it could be malware (search/find on the page, it is near the bottom):