All the vulnerabilities related to the version 0.3.4 of the package
Reverse Tabnabbing in showdown
Versions of showdown prior to 1.9.1 are vulnerable to Reverse Tabnabbing. The package uses target='_blank' in anchor tags, allowing attackers to access window.opener for the original page when opening links. This is commonly used for phishing attacks.
Upgrade to version 1.9.1 or later.