In Hacked Sites Troubleshooter - Search Console Help, there is a tutorial to find hacked content:
Use the Fetch as Google tool in Webmaster Tools to check suspicious pages for hacked content.
Hackers often try to hide hacked content on your site to prevent it from being easily removed. Even if a page appears normal or even removed to you, it's possible there is still hacked content on it. When you use the Fetch as Google tool, you see the page as Google would see it. That way you can see if there is any live spammy content on your page.
How can I do this?