Microsoft Excel Spoofing Vulnerability

According to the CVSS metric, user interaction is required (UI:R). What interaction would the user have to do?
Exploitation of the vulnerability requires that a user open a specially crafted file with an affected version of Microsoft Excel and click the security warning prompt to "Enable Content".
In an email attack scenario, an attacker could exploit the vulnerability by sending the specially crafted file to the user and convincing the user to open the file., In a web-based attack scenario, an attacker could host a website (or leverage a compromised website that accepts or hosts user-provided content) containing a specially crafted file designed to exploit the vulnerability.
An attacker would have no way to force users to visit the website. Instead, an attacker would have to convince users to click a link, typically by way of an enticement in an email or instant message, and then convince them to open the specially crafted file.

According to the CVSS metrics, successful exploitation of this vulnerability could lead to major loss of confidentiality (C:H) and major loss of integrity (I:H) but have no effect on availability (A:N). What does that mean for this vulnerability?
An attacker who successfully exploited this vulnerability could trick a user into enabling content, that they are unable to inspect, which enables an attacker to view or alter data. However, this vulnerability would not allow an attacker to deny any function.

Is the Preview Pane an attack vector for this vulnerability?
No, the Preview Pane is not an attack vector.

According to the CVSS metric, the attack vector is local (AV:L) but no privileges are required (PR:N) and user interaction is required (UI:R). How could an attacker exploit this spoofing vulnerability?
The attack itself is carried out locally by a user with authentication to the targeted system. An attacker could exploit the vulnerability by convincing a victim, through social engineering, to download and open a specially crafted file from a website which could lead to a local attack on the victim computer.

Security updates
https — https://docs.microsoft.com/en-us/officeupdates/microsoft365-apps-security-updates
16.0.5387.1000 — https://support.microsoft.com/help/5002351
15.0.5537.1000 — https://support.microsoft.com/kb/5002348
15.0.5537.1000 — https://support.microsoft.com/help/5002348