In order to change the password, you need to enter the old one. Admittedly the pop-up is stupid, but it doesn't have serious consequences. Anyhow, having physical access to a machine lets you do whatever you want with its contents, unless the disk is encrypted with BitLock
"If those who say bad things about me knew what I think of them, they'd say even worse." (Sacha Guitry)
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"Earth is the cradle of mankind. Nobody can live in the cradle forever" (Constantin Tsiolkovski)