This vulnerability is highly dangerous and expected to become exploited.
This could allow a malicious actor to upload any type of file to your website. This can include backdoors which are then executed to gain further access to your website.
CVSS score is a way to evaluate and rank reported vulnerabilities in a standardized and repeatable way but which is not ideal for WordPress.
We advise to mitigate or resolve the vulnerability immediately.
Update to version 1.3.9.6 or later to remove the vulnerability. Patchstack users can turn on auto-update for vulnerable plugins only.