I didn't put the password to enter the Mikrotik and after a couple of days the Mikrotik asks me for the password ... and I can't even log in with the Mac, I have to reset ...
I don't understand how this can happen? is it a Mikrotik bug ... or ... do they come in and change the parameters?

Someone did, since you left an unsecured router accessible!

if you connect your mikrotik with no password the hakers will change the password in few moment, and the Searchers tell the community must people change password before connect the milrotik with internet

Someone changed it... always secure your router...

2 new Golden Rules for every device:
1. If there is no default password, create one in first login.
2. If there is a default password, change it in first login.

Ryosaeba , what version of ROS was your Mikrotik router running ?
Not so long ago, some of the older versions also had a vulnerability where a remote hacker could gain access to a Mikrotik no-matter-what-password-you-had.

North Idaho Tom Jones