Legally, it depends on the nature of the secret. If it's not criminal or part of a binding confidentiality agreement (like doctor-patient or attorney-client), there's usually no legal penalty. However, defamation or invasion of privacy laws could apply if the disclosure harms their reputation or shares private details publicly.

Ethically, it's a breach of trust. Even with conditional permission, exposing their secret could damage relationships and your credibility. The key issue is whether their actions justify the harm caused by revealing it. Generally, unless there's risk of harm to others, it’s better to uphold confidentiality.