Attackers can use your server infrastructure to host fraudulent pages designed to steal bank details or login credentials from unsuspecting internet users. Data Breaches and User Privacy Risks

If your forum processes any payments, subscriptions, or donations, a compromised theme can act as a keylogger, capturing credit card information or payment gateway API keys. A data breach can permanently destroy your community's reputation and potentially expose you to legal liabilities under data protection regulations like GDPR or CCPA. Search Engine Penalties and SEO Devaluation

Nulled themes are rarely distributed out of charity. Attackers use them as delivery vehicles for malware.