As immediate action, update the affected plugin. If you're unable to do so, ask your hosting provider or web developer for help.
Attackers can inject malicious scripts into the site that steal visitor data or hijack their accounts.
CVSS score is a way to evaluate and rank reported vulnerabilities in a standardized and repeatable way but which is not ideal for WordPress.
This security issue has a low severity impact and is unlikely to be exploited.
Patchstack has issued a mitigation rule to block any attacks until you have updated to a patched version.
Update to version 18.4 or later to resolve the vulnerability. Patchstack users can turn on auto-update for vulnerable plugins only.