On Thursday, shares of Yahoo Inc. are down about 5.3% in afternoon trading after reports have surfaced that Verizon (VZ Quick QuoteVZ - Free Report) is weighing doubts on its deal to acquire the internet company for $4.8 billion following news of another security breach, likely Yahoo’s largest in its history.

"As we've said all along, we will continue to evaluate the situation as Yahoo continues its investigation," Verizon said in the statement Wednesday. "We will review the impact of this new development before reaching any final conclusions."

"We are confident in Yahoo's value and we continue to work toward integration with Verizon," a spokesperson for Yahoo said in a statement.

Yahoo’s latest security breach, which it disclosed yesterday, may have affected over one billion accounts, dating back to 2013. It is thought to be separate from another cybersecurity incident Yahoo experienced this past September, which affected around 500 million accounts.

Verizon may use this breach to renegotiate the terms of the original acquisition deal, as there is now potential for lawsuits, user decline, and more damage to Yahoo’s brand. The communications giant agreed to buy Yahoo back in July with the goal of utilizing Yahoo’s large audience to compete for online advertising sales against giants like Facebook and Alphabet (GOOGL Quick QuoteGOOGL - Free Report) .

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