The firm said it took down the link for credit report assistance temporarily "out of an abundance of caution".
Equifax's stock plunged at the news of the latest breach, a Wall Street Journal reporter noted on Twitter.
Equifax shares dropped as much as 3.5 percent Thursday after it said it has disabled one of its customer help online pages and is investigating another possible cyberbreach.
The Equifax may have been hacked again, now to serve up adware. Many websites use analytics companies to track people who visit their sites.
Hackers reportedly altered Equifax's credit report assistance page that would send users malicious software pretending to be Adobe Flash.
Since news of Equifax's massive data breach broke last month, the company is facing investigations in Canada and the US, as well as at least two proposed class actions filed in Canada. The hack has led to multiple federal and state investigations and the departure of the company's 12-year chief executive.
"Despite early media reports, Equifax can confirm that its systems were not compromised", Marisa Salcines, a spokeswoman for the company, said in a statement. (Much less on web pages specifically designated to help the victims of previous hacks.) Most companies whose primary goal is to collect and secure highly sensitive (and incredibly lucrative) data invest in, you know, basic security measures.
In early October, Equifax revised the number of consumers potentially impacted in the breach - bumping up the total in the U.S.to 145.5 million and reducing the number in Canada from an estimated 100,000 to 8,000.