Webmin password_change.cgi Backdoor

This module exploits a backdoor in Webmin versions 1.890 through 1.920.
Only the SourceForge downloads were backdoored, but they are listed as
official downloads on the project's site.

Unknown attacker(s) inserted Perl qx statements into the build server's
source code on two separate occasions: once in April 2018, introducing
the backdoor in the 1.890 release, and in July 2018, reintroducing the
backdoor in releases 1.900 through 1.920.

Only version 1.890 is exploitable in the default install. Later affected
versions require the expired password changing feature to be enabled.