Microsoft Defender's False Positive on DigiCert Certificates - 2026
In late April 2026, Microsoft Defender's signature update erroneously identified legitimate DigiCert root certificates as Trojan:Win32/Cerdigent.A!dha, leading to widespread false-positive alerts and the removal of these certificates from Windows trust stores. This misclassification disrupted SSL/TLS validation and code-signing operations across numerous systems. Microsoft addressed the issue by releasing Security Intelligence update version 1.449.430.0, which corrected the false positives and restored the removed certificates. This incident underscores the critical importance of accurate threat detection mechanisms and the potential operational disruptions caused by false positives. It also highlights the necessity for organizations to have robust incident response plans to swiftly address and mitigate such issues.
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