Webmin 2.510 is vulnerable to a Host Header Injection in the password reset functionality (forgotsend.cgi). The reset link sent to users is constructed using the HTTP Host header via getwebminemailurl(). An attacker can manipulate the Host header to inject a malicious domain into the reset email. If a victim follows the poisoned link, the attacker can intercept the reset token and gain full control of the target account.