CCleaner Users began posting emails they had received from the program developer alerting them to a recent security problem on the forums.

The MOVEit Transfer flaw, according to CCleaner, affected it and gave hackers access to some of its users’ data.

A forum member posted a remark that said, “We recently discovered that as a customer of CCleaner, some limited personal information of yours was exposed on the dark web.”

On the software community site, a member asked if CCleaner really sent these kinds of emails. One of the forum administrators said that it was a scam email and advised users to disregard it.

The CCleaner stated, “We discovered some of our customers’ personal information, including name, email address, and phone number, was also impacted during ongoing due diligence.”

A spokesman for CCleaner stated that the company will provide free dark web monitoring services to anybody who are impacted.

Avast, a cybersecurity business, owns Piriform Software, the developer of CCleaner. With more than five million desktop installs and over 2.5 billion downloads, the well-known tool is in high demand.

In 2017, a trojan horse that installed backdoors was used to infect CCleaner. The software’s backdoor gave hackers access to millions of devices.