Which of the following represents a breach of the GDPR related to personal data processing?

The scenario of failing to report a data breach indeed represents a breach of the GDPR as it undermines the principles of transparency and accountability that the regulation aims to uphold. Under the GDPR, organizations are mandated to report certain types of personal data breaches to the relevant supervisory authority, usually within 72 hours of becoming aware of the breach. This requirement exists to ensure that individuals whose data may have been compromised are informed and can take appropriate action to protect themselves.

In contrast, enforcing penalties pertains to compliance and is not a breach itself. It is the regulatory authority's action in response to breaches of the GDPR. Transferring data without consent is a serious violation regarding data subject rights and the lawful basis for processing under the regulation, but the specific focus of the question is related to breach reporting obligations. Similarly, not honoring data subject requests is also a serious issue; however, the question specifically targets failure to report breaches, which is a distinct requirement outlined in the GDPR.