Microsoft Releases Windows 10 Insider Preview Build 21390 for Insiders

Step 3: Clean Install (Recommended)

  1. Backup your data.
  2. Boot from the USB (press F12/Del during startup).
  3. When selecting partition type, delete all existing partitions if you want a pure system.
  4. Let Windows setup run – it will take 15-30 minutes.

4. Security & Malware Risk Assessment

High Risk (9/10) – Not suitable for any production or personal daily use.

| Threat Vector | Description | |---------------|-------------| | Pre-ransomware vulnerability | Unpatched SMB, RDP, and printer spooler exploits | | Timebomb activation | System becomes unusable or resets every few hours | | Telemetry from Microsoft | Insider builds still send diagnostic data | | Trojanized ISOs | Attackers embed backdoors (e.g., modified install.wim with hidden admin account) | | Expired certificates | Drivers and apps may fail to install or run | | No Windows Update | Cannot get any security fixes, even for Defender definitions (unless manually updated via offline .cab) |

Build 21390: Released on June 17, 2021