What happened 

Shares of Criteo (CRTO -0.54%), an online advertising company, climbed 12.5% this week, according to data provided by S&P Global Market Intelligence, after it reported revenue that was higher than expected for the fourth quarter.

Investors also drove the adtech stock higher this week on rumors that Criteo may be putting itself up for sale. 

So what 

Criteo reported non-GAAP (adjusted) earnings per share of $0.84 in the quarter, which was down 42% year over year and missed Wall Street's consensus estimate of $0.97 per share. 

The company's sales also declined in the quarter, falling 14% to $564 million, but investors were happy to see that Criteo's revenue outpaced analysts' average estimate of just $277.2 million. 

But the big catalyst driving Criteo's share price up this week came from a Reuters report that said that the company is considering putting itself up for sale. 

The reporting said that Criteo began the process of looking for buyers last week and has hired the investment bank Evercore to help with a potential sale. But no deal is certain and the company hasn't commented on the rumors at this point. 

Companies that are acquisition targets often get a lot of attention from investors as they snatch up shares and then hope for a quick sale. Criteo investors may be extra hopeful for a sale right now because the advertising market has been a bit difficult lately. 

As the online advertising industry moves away from online trackers, called cookies, some investors have become worried advertising companies won't be able to fully adapt to the changes. 

Now what 

Investors should tread lightly with Criteo's stock right now based on acquisition hopes. There's nothing certain yet about the company putting itself up for sale and even if it does Criteo may not find a buyer. 

That doesn't mean that Criteo is a bad investment, but it does mean that buying the stock right now on the hopes that Criteo will be sold would be a highly speculative move.