A security patch released by Microsoft last month failed to fully fix a critical flaw in U.S. tech giant's SharePoint server software that had been identified in May, opening the door to a sweeping global cyber espionage operation.

The tech giants have evidence that Chinese hackers are exploiting the new bug, but warned "multiple actors" are also hacking into affected SharePoint systems.

At least 54 organizations have been breached in the attacks. Some of the attacks that targeted organizations using an exploit in Microsoft’s SharePoint server platform over the last few days have been linked to hacking groups affiliated with the Chinese government, according to a new Microsoft security blog.