https://www.worklawyers.com/job-references-hiring-california/

And, if the information was given without being requested by the potential employer,
it is strong evidence that the statement is false or made with the intent to prevent the employee from being hired. If that is the case,
the former employer may have broken the law by volunteering the information.


Malicious Statements
If a statement is made by a former employer with malice, the common-interest privilege protecting the employer’s reference does not arise.
The California Supreme Court has defined malice in this context as a state of mind arising from hatred or ill will, which evidences a willingness to injure another person.