Over the weekend, Google issued many manual actions for “unnatural outbound links.” This is a penalty issued by the Google manual actions team, specifically over websites linking out to other sites in an effort to manipulate the Google search results. In this case, it seems Google penalized the site by deciding not to trust any of the links on the website.
Google sent out outbound link penalties over the weekend through emails. To see if you have got the email, check your Google Search Console message center. The content of the email was as follows:
“If you see this message on the Manual Actions page, it means that Google has detected a pattern of unnatural artificial, deceptive, or manipulative outbound links. Buying links or participating in link schemes in order to manipulate PageRank is a violation of Google’s Webmaster Guidelines.
As a result, Google has applied a manual spam action to the affected portions of your site. Actions that affect your whole site are listed under Site-wide matches. Actions that affect only part of your site and/or some incoming links to your site are listed under Partial matches.”
You should log into your Google Search Console account and check your all messages box to see if you have this notification, or any others. A representative of Google confirmed that this was related to bloggers posting reviews in exchange for free products.