A number of times now, when visiting unfamiliar web pages, I have experienced PDF files trying to download themselves. The pages themselves are not PDF files, they are not the sort of page where you would expect to find PDFs (e.g., it has happened on soft porn sites, and most recently, today, on what I think was some sort of humor site - I am not quite sure as I got out quickly), and I did not click anything on the page to cause the download: it seemed to occur just from loading the web page.
I am concerned that these might be some sort of malware, although I have not had any obvious malware symptoms, and I have scanned after the incidents with both McAfee and with the free version of Malwarebytes Anti-Malware and found nothing (on previous occasions I have tried AdAware and AVG as well). It may be that I am protected from the exploit (if that is what it is) either because I am using Firefox (under Windows XP), or, more likely, because I do not use Adobe Acrobat Reader as my default PDF reader (I use PDF-XChange Viewer). Thus, if this is something designed to exploit a bug in Adobe Reader, it might be safe in XChange Viewer. The file I got today loaded up in PDF-XChange Viewer and appeared as a single blank page (I think - I closed it quickly, and I am not anxious to open it again). However, the file from earlier today is now still sitting on my desktop, and neither McAfee or Malwarebytes seem to be bothered by it.
So, does anyone know what might be going on? Is it malware? Am I infected? Or am I freaking out over nothing?
Incidentally, the file that downloaded today is called f.cgi.pdf and is 11.9K in size. The page it came from was www. uncoached. com/2009/08/14/the-one-thing-better-than-a-knockout-is-a-double-knockout/ [Link deliberately broken, I do not recommend that you go there.]