Security researchers at Google and Microsoft say they have evidence that hackers backed by China are exploiting a zero-day bug in Microsoft SharePoint, as companies around the world scramble to patch the flaw.
The bug, known officially as CVE-2025-53770 and discovered last weekend, allows hackers to steal sensitive private keys from self-hosted versions of SharePoint, a software server widely used by companies and organizations to store and share internal documents. Once exploited, an attacker can use the bug to remotely plant malware and gain access to the files and data stored within, as well as gain access to other systems on the same network.
This is a zero-day bug though?
It’s not, the title lies.
Read the article
I did… It looks like the bug has been exploited for a couple of weeks now, with a patch only being released on 20th of July? That makes it zero-day
Edit: realised we might have different definition of zero day. Depends whether you consider that the vendor didn’t know about the issue, or there isn’t a patch available upon exploitation of the vulnerability.
Zero day is typically defined as there being zero days since the vulnerability is known to the developer, in other words, it being unknown at the time of the exploit.
https://en.wikipedia.org/wiki/Zero-day_vulnerability?wprov=sfla1
Ah thank you. I thought zero day and 1 day vulnerabilities were: 0-day = vulnerability is not known to the vendor and so there is no patch. If exploited, it is a 0-day attack. 1-day = vulnerability is known and patch is available, but not all systems are patched.
I.E. the actual number of days doesn’t matter.