Microsoft SharePoint Server Spoofing Vulnerability

According to the CVSS metric, user interaction is required (UI:R) and privileges required is Low (PR:L). What does that mean for this vulnerability?
This means an authenticated user can upload malicious content, but exploitation only occurs if they convince another user to visit or interact with that content.

According to the CVSS metrics, successful exploitation of this vulnerability could lead to some loss of confidentiality (C:L), and integrity (I:L) but lead to no loss of availability (A:N). What is the impact of this vulnerability?
An attacker who successfully exploited the vulnerability could view some sensitive information (Confidentiality), make changes to disclosed information (Integrity), but cannot limit access to the resource (Availability).

There are multiple update packages available for some of the affected software. Do I need to install all the updates listed in the Security Updates table for the software?
Yes. Customers should apply all updates offered for the software installed on their systems. If multiple updates apply, they can be installed in any order.

Security updates
16.0.5548.1003 — https://support.microsoft.com/help/5002861
16.0.5548.1003 — https://support.microsoft.com/help/5002862
16.0.10417.20114 — https://support.microsoft.com/help/5002854
16.0.10417.20114 — https://support.microsoft.com/help/5002856
16.0.19725.20210 — https://support.microsoft.com/help/5002853