If you got some simple free hosting boards it's quite easy, you go to your administraction control panel, go to memberlist or search members and find ANT_Mlekce, you can edit his profile entirely, you won't see his current password since it's encrypted and you won't ever find it out, however you can change it to whatever you want and then save his information, the password you then set will be his log-in and he can edit it again if he wants.
Only by hacking the website you'll be able to get his actual password but it's pretty secure nowadays.
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