The article discusses the challenges faced by blockchain technology in terms of scalability, security, and privacy protection. It highlights the limitations of current blockchain applications and the risks they pose to investors and sensitive data. Various research directions are proposed to address these bottlenecks, including improving consensus mechanisms, sharding the network, and enhancing security through cryptographic technology. The article also provides a summary of 11 high-quality papers accepted for a special issue, covering topics such as smart contract vulnerability detection, graph-based sharding schemes, NFT security, and decentralized reputation management mechanisms.