User-Agent: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2a1pre) Gecko/20081215 Minefield/3.2a1pre Build Identifier: Mozilla/5.0 (Windows; U; Windows NT 5.1; en-US; rv:1.9.2a1pre) Gecko/20081215 Minefield/3.2a1pre upon opening/downloading a .c file, firefox will infinitely create new tabs. Reproducible: Always Steps to Reproduce: 1. click above URL 2. Browse and select firefox as application to open .c files 3. check 'remember' ... 4. Hit OK --> firefox will infinitely create new tabs. I also noticed 2 more ff threads starting up. Actual Results: infinite tab creation Expected Results: displayed the c file text, probably with default text MIME type.

You get a download dialog because Firefox can not display the Mime-type, you select to open this mime-type with Firefox, the called Firefox can not handle the file itself and looks for the configured helper apps and you had Firefox definied, that means Firefox gets openened..... (recursion). This is a dupe of 2 bugs : a) don't allow to select Firefox as helper application b) convert a mime/type X to plain/text and view it in Firefox