According to people on social media, Facebook could be adding a “dislike” button.  Mark Zuckerberg said in a conference that this social trend is not true and that this is a “scam”.

The scam circulating on Facebook prompts users to click to "get newly introduced Facebook dislike button” on your profile.

This is classic scam stuff.  Facebook wouldn't make you jump through hoops to activate a new feature. Attackers use the colors and logos of companies to make their fake sites look real. Their links may trick users into sharing personal information or downloading malware onto their machines.

Zuckerberg made it clear that the company is not using the word "dislike".  It is looking into a button that lets people show empathy in circumstances when "like" just isn't appropriate, such when a friend posts bad news.