Affected versions of this package are vulnerable to Open Redirect due to the implementation of URL encoding using encodeurl before passing it to the location header. This can lead to unexpected evaluations of malformed URLs by common redirect allow list implementations in applications, allowing an attacker to bypass a properly implemented allow list and redirect users to malicious sites.
Remediation
Upgrade express to version 4.19.2, 5.0.0-beta.3 or higher.