Go to Microsoft account > security > Password security. For security reasons, You have to verify your identity with a security code. Choose if you want to receive the security code by mobile or email. You will be asked to verify your email id or the last four digits of your mobile number, and then click on Send code. When you receive it, enter the code and click on submit. Type your current password > Type your new password > Save. Tip: If you can not get the code by mobile or email, you have to enter an email id that's different from the one you are trying to recover. Go to Recover your account page and follow the prompts.
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