HeidiSQL solution for SQL Server error 18488?
You can change the password from sqlcmd using -z or -Z:


  -z new_password Change password: 

sqlcmd -U someuser -P s0mep@ssword -z a_new_p@a$$w0rd

  
  -Z new_password Change password and exit: 

sqlcmd -U someuser -P s0mep@ssword -Z a_new_p@a$$w0rd