microcode updates are supposed to address:

• Security issues
• Stability issues (voltage/thermal-related)
• Incorrect processor behavior (which could cause unpredictable program behavior, hangs, crashes, reboots, memory corruption, incorrect calculations, etc)
• very rarely, additional functionality

A potential security vulnerability in CPUs may allow information disclosure. Intel is releasing Microcode Updates (MCU) updates to mitigate this potential vulnerability.

For details see: https://www.intel.com/content/www/us/en/security-center/advisory/intel-sa-00233.html