Although Microsoft Defender has a good reputation since its launch and is quite helpful in computer security, every once in a while it will start to go rogue. The most common situation is that it will inexplicably mark legitimate files or URLs as malicious files or malicious links. This time the “attack” is a familiar formula and a familiar taste. The old problem has come back again. Microsoft has also confirmed the existence of this problem.

Microsoft Defender goes rogue again, legitimate files and links are once again misreported as harmful
In the past two days, system administrators of various companies have been extremely busy. They have received a large number of email notification security alert emails from Microsoft Defender flagging malicious files and malicious links. On Microsoft 365 Status’s Twitter, the company has announced the bug and provided more details about the bug, which can be tracked in the Microsoft 365 Admin Center under the codename “DZ534539.”
We’re investigating an issue where legitimate URL links are being incorrectly marked as malicious by the Microsoft Defender service. Additionally, some of the alerts are not showing content as expected. Further details can be found under DZ534539 within the admin center.
— Microsoft 365 Status (@MSFT365Status) March 29, 2023
On Reddit, IT and system administrators around the world are also discussing this issue. In one of the threads, netizen x-64 shared detailed information about DZ534539:
Comment
by u/x-64 from discussion Microsoft Defender Issues
in sysadmin
Now, Microsoft has tweeted more about the issue at Microsoft 365 Status, where the company said:
We determined that recent additions to the SafeLinks feature resulted in the false alerts and we subsequently reverted these additions to fix the issue. More detail can be found in the Microsoft 365 admin center under DZ534539.
— Microsoft 365 Status (@MSFT365Status) March 29, 2023
It appears that the issue is a bug in the Safe Links feature of Office 365 Defender’s malicious scanning feature. Although Microsoft announced that it is aware of this problem, it is still trying to deal with it, and the fix update has not yet been released. Therefore, many netizens also reported that this situation still exists, and everyone can only wait for Microsoft to release an update to fix it.
Source: KOCPC Chinese