Half an hour ago, I was on the home page and was interested in clicking on to a (Washington politics) news story (I right-clicked and used "Open in a Second Tab" [paraphrase] to open the story [I am using Mozilla Firefox]). But when the new tab opened, there was no sign of that news story at all. Instead, I saw a different version of the Yahoo home page, consisting of a different collection of news stories, all of them tabloid-ish and "feature stories", not anything remotely connected with serious news stories (like the Ukraine or Washington politics or the disappeared plane) of any kind.
That isn't all. The URL for this wrong page was brb.yahoo.com, and in place of the central news photo that is always toward the top of the Yahoo home page, there was instead a rather amateurish-looking advertisement in that same big "box" with a "poor-man's-type-font" message on the right [it may have been Courier type?]!
I figured at first this might be a virus on my Windows PC, so I tried System Restore, bringing my system back to Tuesday................... This time, after rebooting, when I tried to get into "yahoo.com", I didn't even get to any home page at all. Instead, I got to the same mysterious URL, brb.yahoo.com, but with a totally different thing on the screen from before: a big message on the screen to the effect that it was now unable to comply with my request for the Yahoo page (It even suggested I might disable my cookies prevention and that that might allow the page to appear.........NO THANKS!!).
By sheer luck, I then thought of going into Google (which did come up successfully) and of searching for refs. to brb.yahoo.com. That's how I found your discussion. Thank goodness! In fact, THAT WAS THE ONLY WAY I WAS THEN ABLE TO SIGN IN TO MY YAHOO ACOUNT (phew)! (I couldn't go in via the Yahoo home page, after all.)
That's most of my story -- HOWEVER:
Earlier this morning, just minutes before my very first rebuff on that first politics news story that started all this, even before my subsequent System-Restore and the ensuing reboot, I had uploaded, first thing, an apparent Update for my Mozilla Thunderbird e-mail ap. So I'm wondering, please, did anyone else here also have occasion to upload any Update of some kind to one of your own aps just minutes before first encountering your Yahoo problems?
If that is what has happened with all of us, then I'm afraid that it really is a nasty virus in all our own PCs right now and we've all become infected with it, and a System Restore cannot erase its effects -- that's how nasty this virus is! But if none of you had any Update episode with any of your aps shortly before encountering your Yahoo problems, then my own Update experience with Mozilla Thunderbird is just a red herring, just a coincidence (thank goodness), and so we can assume this is a bad glitch right inside Yahoo that doesn't involve our PCs -- perhaps a Yahoo glitch brought on by hacking, perhaps by something else.
Bottom line: Did anyone else here -- please! -- recently install an Update for one of your aps? Knowing your answers to that question could be very important to knowing if there is now a serious infection in all of our PCs, or if the problem is only with Yahoo.