Hundreds of customers of digital authentication firm Okta have possibly been affected by a security breach caused by a hacking group known as Lapsus$, the company said.

The breach has sparked concern since the cyber-extortion gang posted what appeared to be internal screenshots from within the organisation’s network earlier this week.

In a series of blog posts, chief security officer David Bradbury said the “maximum potential impact” was to 366 customers whose data was accessed by an outside contractor, Sitel. The contractor employed an engineer whose laptop the hackers had hijacked, he added.

The 366 number represented a “worst-case scenario”, Bradbury cautioned, adding that, in any case, the hackers had been constrained in their range of possible actions.

Okta, based in San Francisco, helps employees of more than 15 000 organisations securely access their networks and applications, so a breach at the company could lead to serious consequences across the Internet.

Bradbury said the intrusion would not have given “god-like access” to the intruders as they would have been unable to perform actions such as downloading customer databases or accessing Okta’s source code.

Okta first got wind of the breach in January, he added, while the Miami-based Sitel Group only received a forensic report about the incident on 10 March, giving Okta a summary of the findings a week later.

Bradbury said he was “greatly disappointed by the long period of time that transpired between our notification to Sitel and the issuance of the complete investigation report”.