The news site Ars Technica, citing an independent security analyst, reported visitors to the Equifax site were being tricked into downloading an "adware" program which, when installed, delivers unwanted marketing messages.
The firm said it took down the link for credit report assistance temporarily "out of an abundance of caution".
The company said the problem is in its credit report assistance link on its website.
The incident comes just over a month after Equifax disclosed a massive data breach in which hackers stole the personal information of more than 145 million USA consumers.
The September 7 hack was a biggie: Criminals were able to gain access to names, Social Security numbers, birth dates and addresses.
Somehow, the worst credit-card-data breach in USA history just got worse. The latest claims reveal that after one of the largest data breaches ever, Equifax still may not have learned its lesson about providing proper security for its customers.
Money expert Clark Howard says rather than waiting on Equifax to get itself together, consumers should be proactive and do what they can to protect themselves from identity fraud. The hacked page tended to appear when a user attempted to contest incorrect information on their credit report.
The breach led to the retirement of Equifax chief executive Richard Smith, who has remained as a consultant to the company during the investigation.