Q: Baidu Ads and Browser Hijacking

Hope someone can help me with this; I recently went to China for a biz trip and when I was there, all the US websites I went to: The Verge, Gamespot, and ESPN showed ads from Baidu and other chinese ad providers.

However, when I returned to my home country, the ads all remained. On top of that, the ads are now in BOTH my browsers Safari and Google Chrome.

The Ads sit on the bottom right of my browsers and look like this:

To make matters worse, when I try to open up a new tab, *********** now pops up instead. I use my computer for work and this is unacceptable. I'm starting to worry that my whole mac may have been hacked.

Firstly, I only logged on to the hotel Wifi. I didn't install any new programs or extensions when I was in China.

Secondly, I only used the above websites during my trip. I was too busy to use it for anything else other than websurfing and microsoft Outlook.

Can anyone help?