See the question and my original answer on StackOverflow

If the errors are caused by malware or spyware rogue extensions (especially those trying to spy on facebook account/pwd), which is perfectly possible, and this will happen anyway in the wild world, there is basically nothing you can do.

The best you can do is validate your site on various standard installations and browsers, including standard 3rd parties (like Adobe's flash, etc.), and add a help pages on your site to help your end user sort these kind of problems out by themselves.