Threats & general security
What is Zero-day?
A zero-day is a software flaw that attackers are exploiting before the vendor has released a fix — defenders have had "zero days" to patch. They are prized by attackers and unavoidable by definition, which is why a layered defence (least privilege, segmentation, monitoring, rapid patching once a fix lands) matters more than chasing any single bug. Once a fix ships, the unpatched window is on you.