my e-mail ?hacked with malware

I had signed into one of my Yahoo e-mail accounts with no issues and I was in my inbox and I reviewed what was in my inbox, I think I  opened a few e-mails and read them from individuals or organizations I normally get e-mails from and trust, and everything was fine.  I then noticed that there were 11 e-mails in my spam folder and I always delete the e-mails in the spam folder before I sign out of my Yahoo e-mail account. I clicked on the spam folder icon to go to my spam folder to, "check all" and, "delete all" of the e-mails in my spam folder.  The screen did not take me to my spam folder, instead a red/orange webroot warning screen came up informing me that the next screen contained malware, and asked me what I wanted to do.  I clicked on, "get me out of here" and the browser closed.  I was puzzled because I was already in my Yahoo mail acct. and all I was doing was going from the inbox to the spam folder.  I opened my browser (firefox) and resigned  into the same yahoo mail acct. inbox with no issues, and this time I did not open any e-mails in the inbox but clicked on the spam folder icon to delete the spam folder.  Again the same message webroot danger came up.  This time I clicked on the, "continue anyway" icon on the webroot warning, thinking I would go to my spam folder, and if I did not open any spam e-mails, which I never do, I would beable to delete them and that would be it.  It did not take me to my spam folder though, instead a full screen picture of a tatooed naked biker chick standing  next to a Harley popped up on the screen.  I immediately closed the browser.  I have scanned my computer 3x with webroot since yesterday and all the scans are clean.  Should I change the password on that Yahoo acct. or just let it die? Do you think I have been hacked?  I went into the same e-mail account afterwards yesterday and again today with no issues.  Yesterday I was able to delete all the spam e-mails and I went to the spam folder from the inbox with no problems.  Any suggestions?