Privacy leakage in blockchain technology research focuses on identifying and mitigating scenarios where sensitive information can be inferred or exposed despite the decentralized and pseudonymous nature of blockchain systems. Research papers in this area analyze vulnerabilities arising from transaction traceability, address clustering, smart contract interactions, and metadata analysis, which can lead to the disclosure of user identities, transaction patterns, or confidential business data. Studies also explore attacks such as deanonymization, linking attacks, and side-channel exploits that compromise privacy in public, consortium, or hybrid blockchains. To address these challenges, researchers propose privacy-enhancing techniques including zero-knowledge proofs, ring signatures, confidential transactions, homomorphic encryption, and off-chain computation, as well as privacy-preserving consensus and data-sharing protocols. Key considerations include balancing transparency with confidentiality, scalability of privacy mechanisms, and integration with existing blockchain infrastructures. Overall, this body of research aims to strengthen blockchain systems by preventing unintended data leakage while maintaining trust, security, and functional efficiency.