Well, some of us had this problem. Here is how to get rid of it.
1. The problem was: When we start Firefox
https://hao.360.cn/?src=lm&ls=n...
is on the opening page. We've gone through Malware/anti-virus scans and a few other things like deleting old, useless software, but it doesn't help. The we found out a good idea.
2. The good (and simple) idea (solution) was -- to delete the shortcut and to create a new one! How to do it:
a) Delete your old shortcut, because it's infected.
b) Create a new one.
(If you don't know how to, here is the way: To create a new shortcut, you can go to the Windows Start menu, search box, and paste the following (C:\Program Files\Mozilla Firefox\), then press Enter to load it. (If you have your Mozilla Firefox installed in D:\ or E:\, of course, you should search it in there.) That should launch the Firefox program folder. Then right-click the firefox.exe and select "Send To the Desktop" (it creates a shortcut).
Pretty easy solution, isn't it?