To: wily who wrote (4700 ) 7/27/1999 12:39:00 AM From: mr.mark Respond to of 110648
from an email i received today... "IE5 Weirdness #1: The FavIcon Mystery (and Security Hole) Reader Brian Dillree was the first of several readers to ask a question about an increasingly common practice: Fred, I'm hoping you can help me on this one.It has me and a couple other people stumped. How do some websites insert their own icon into ie5 internet shorcuts? If you don't know what I mean, go to deja.com (for example) and create a shortcut to it either on your desktop or right in the ie5 toolbar and the standard ie5 icon is replaced with the deja.com icon. How is this possible?? Thanx in advance Brian Dillree If a web designer creates a special icon for a web page, makes it 16x16 pixels in size, uses 16 colors, and names it "favicon.ico," then when you either put that page on your favorites list or create a shortcut on your desktop, IE5 will use the "favicon" icon in place of the standard dog- eared web page IE5 icon. Lots of web sites are doing this now as a way to customize their look and to help make their pages stand out from the crowd. But there can be a problem: As Microsoft puts it, "A specially-malformed icon could overrun the buffer and be used to run arbitrary code on the user's computer." By which they mean someone could hack your system and run whatever software they wanted. About 60 days ago, Microsoft released a patch for this "vulnerability;" If you've been keeping up with all your updates and fixes, you probably already have this one. But if not--- check outmicrosoft.com But there's another snag: It's theoretically possible for a web site to track which IP address is calling for the favicon.ico. This isn't exactly a gaping security hole, but it is at least theoretically possible for a site owner to figure out which IP addresses are bookmarking his or her site. It would be somewhat easier for the site to build a log of your bookmarks if you let the site set a cookie, or if you registered upon entry. I mention low-risk security hole this in the interests of completeness, but I also have to say I think the odds of anyone going to that amount of hassle just to see if you bookmarked a page on their site are quite remote. And even if they did know what you bookmarked from their site, so what? Note that there's no way for a favicon to be used to snoop your other bookmarks, or to see what you bookmark on other sites. So this is a mostly theoretical problem--- and a tiny one at that. But the "malformed favicon" issue is more real--- grab the patch, if you haven't already."