You likely didn't install this manually. It usually arrives in one of two ways:
4.20.9818.0 is an older sub-version of SP2. Even the "newer" SP3 (version 4.30.2100.0) is also now unsupported. 🛠️ Why is it on your computer? Microsoft Msxml 4.20.9818.0
Because it no longer receives updates, it is frequently flagged by security scanners (like Nessus or Qualys) as a vulnerability. You likely didn't install this manually