Microsoft is disputing just how big its customer data leak was

Microsoft said Wednesday that an unspecified amount of customer data, including contact info and email content, was recently left exposed to potential access over the internet as a result of a server configuration error.

Cybersecurity vendor SOCRadar, which reported the data leak to Microsoft, said in a blog post that data belonging to more than 65,000 companies was affected. Microsoft, however, said in its own post that SOCRadar "has greatly exaggerated the scope of this issue."

Microsoft didn't disclose specifics around the number of companies whose data may have been exposed in the leak or the amount of data involved.

The server misconfiguration was reported on Sept. 24, and the impacted server was "quickly secured" after that, according to Microsoft. Due to the configuration error, there was a potential that certain "business transaction data" could have been accessed without a need for authentication, Microsoft said.

The data corresponds to "interactions between Microsoft and prospective customers," including around the planning and implementation of Microsoft services, the company said in its post.

Affected data may have included "names, email addresses, email content, company name, and phone numbers, and may have included attached files relating to business between a customer and Microsoft or an authorized Microsoft partner," Microsoft said.

SOCRadar said that a "single misconfigured data bucket" was responsible the exposure of the data of the 65,000 affected companies, which the company said are based across 111 countries. The leak amounts to 2.4 terabyte of data, including 335,000 emails, and it involves more than a half million users, according to SOCRadar. The files are dated between 2017 and August 2022, the vendor said.

Microsoft disputed SOCRadar's claims about the size of the leak, saying that an "analysis of the data set shows duplicate information, with multiple references to the same emails, projects, and users."

"We take this issue very seriously and are disappointed that SOCRadar exaggerated the numbers involved in this issue even after we highlighted their error," Microsoft said in its blog post.

The leak didn't involve any vulnerability since it was solely caused by the server misconfiguration, the company said.