How if somebody tells you with proof he found out your passwords? You should immediately change your passwords with better ones then. Below I share with you my experience and several examples & suggestions you can do. Wish you the best!

Background

Several days ago I received a mail that says the sender knows with proof one of my passwords which I use to login to many accounts. His email subject is my password in clear text, let's say, pass123. In security, indeed this kind of password is very easy to crack i.e. in seconds. If I don't change them immediately, this person will be able to login as me and do anything under my name including changing my passwords which in turn will make me unable to login anymore. If similar case happens to you, I strongly suggest you change your passwords immediately as explained below.

What To Do

1. Try to remember your accounts which use that password.

2. Login to one website where that account of yours was registered.

3. Change the password with a secure one.

4. Repeat this process to the other websites accounts you have.

Example

Let's suppose you had a Gmail account which the password is compromised like Background above. What you should do? Login to that account and go to Account Preferences and change password there with a strong one and finally try to logout and login with the new password.

Make Strong Passwords and Keep Them

How to make secure passwords? How to store passwords safely and further open them as you wish at any time? Is it not hard to remember many passwords? A strong password consisted of at minimum 8 characters, letters and numbers, uppercase and lowercase, with a space, with a symbol like # or &, and not containing word found in dictionary. It is of course hard to make and remember all such passwords. Because of that, to create and store passwords in convenient but safe way, today we can use a program. For these two purposes, there is password manager program, such as KeePassXC. 

(Password generator says my password above strength is "Excellent")

For example, to create a password that is strong, we can press Password Generator button in KeePassXC and try to make our own password and program will automatically measure how secure your password is. Alternatively, simply believe password generator creating a new password and use it. 

To save passwords with KeePassXC, read this, it is our tutorial to do that.