The estate agent has not said how many users could have been affected.
London-based estate agency Foxtons are finding out whether hackers have leaked the account details of nearly 10,000 property hunters that are registered with the website.
Foxtons said it had obtained the leaked list and was checking whether the information is genuine or not, according to pcpro.co.uk.
The list, which was said to have been posted anonymously to a popular hacking site PasteBin earlier this week, was reportedly removed.
Titled ‘part 1’, the list suggests that the hackers might be planning yet another cyber attack.
The list is still accessible elsewhere and shows more than 9,800 user names, email addresses and passwords, supposedly registered with MyFoxtons.
The estate agent hasn’t said how many users could have been affected, but it said financial details, including credit card numbers or transaction histories, were safe with third-party providers.
Foxtons, in an emailed statement to its users, said: "It has come to our attention that there were some reports circulating on the internet today suggesting that a small number of user names and passwords to the MyFoxtons web portal were briefly posted to a website.
"We have been able to download the list of usernames and passwords that were posted and are currently running checks to determine its veracity."
As a precautionary measure, the company said it has put in place a system that will reset users’ passwords automatically when they log into the realty site the next time.
An advisory states: "Immediate action…has been taken to safeguard your account and an investigation will continue.
"Should your account be upon the list, you will be contacted directly by our team."