Shares of cybersecurity firm Okta closed down 11.5% after the company said an unidentified hacking group had accessed files that “certain Okta customers” had uploaded to Okta’s support system.

Okta said the hackers were able to access the system using a stolen credential. Okta’s customer offerings, including its production service, were not impacted and are fully operational, the company said.

Some of the largest companies in the world use Okta to streamline their login and identity management systems, including FedEx and Zoom, according to the company.

That makes Okta a high-value target for threat actors, who in a worst-case scenario could hypothetically gain access to dozens of other companies if successful in breaching Okta’s defenses. The breach disclosed Friday does not impact client systems, just a support platform Okta uses to help its clients diagnose issues.

“We have notified impacted customers and taken measures to protect all our customers,” the company said.