A very strange thing started happening a couple weeks ago. I use a lot of different WiFi locations on a daily basis (hotels, restaurants, coffee shops). Starting a couple weeks ago, it happens almost daily that when I connect to a new WiFi location and then start Firefox, I get the "Authentication Required" box that is typical of http-style authentication. Apparently, it is asking me for the username and password for the WiFi router at that location, because I see the IP address of the local router and also a text string that looks like something related to the router. This is very strange because in no case did I enter a URL for any WiFi router. I have Firefox set to start with a blank page. The authentication box comes up before I tell Firefox to do anything, so this is strange because I would expect Firefox not to perform any HTTP transactions when it's supposed to just display the blank page. Also, because this happens upon Firefox startup, before I have a chance to click anything, I do not have the opportunity to invoke any debugger such as with Ctrl-Shift-Q. When I see this box, I just click Cancel, and then the box goes away as expected, and I have the blank page as usual. What I don't see is an "Authentication Required" web page that normally gets displayed when you don't supply the required credentials on an http authentication. This doesn't cause so much of a problem other than a minor inconvenience, but I have to wonder if there's some malware present that's trying to capture router passwords. In any case, it's abnormal behavior because I've never seen this in many years of using Firefox on my computer. I'm running Firefox 39.0 on Windows XP on an IBM Thinkpad X41. I ran a boot-time virus scan using Avast and had no problems reported. I want to know what is causing Firefox to ask me for the WiFi router login credentials. Just to add more info, I think this also happened once on a wired net connection (not WiFi). And it also happened when I had a browser open and connected to a new WiFi location, and then resumed using my browser at that location and suddenly was presented with the auth box (i.e., it was not at Firefox startup time). I should also add that I'm using some add-ons like NoScript and FoxyProxy, but FoxyProxy is generally set to "default" (no proxy). Another weird thing is that the FoxyProxy icon spins upon Firefox startup even though it's only supposed to display a blank page. As I recall, this "premature spinning" phenomenon also occurred long before the weird auth-box symptom started happening.