You discover that a human resource department employee is discussing confidential information with employees outside the department.

Raise it with their manager and ensure it does not happen again. Identify any training needs and ensure everyone understands confiedntiality and the negative impact on performance and morale thee breaches can cause.

if it is related to individual employee, it is a matter of perspective. if it is a general matter that could include other employee without their consent then it is employee confidentiality issue. and should be addressed probably.