International Research Journal of Education and Technology

Blockchain technology has revolutionized decentralized systems by enabling secure and transparent transactions without intermediaries. However, the increasing adoption of smart contracts—self-executing agreements on blockchain platforms—has exposed critical security vulnerabilities, leading to significant financial losses and system exploits. This paper examines key security challenges in blockchain and smart contracts, including attacks, integer overflows, and oracle manipulation. We analyze real-world incidents (e.g., DAO hack, Parity wallet freeze) to highlight the consequences of flawed smart contract design. Additionally, we review state-of-the-art security solutions, such as formal verification tools MythX,Oyente runtime monitoring, and best practices for secure coding. Finally, we discuss emerging trends like Layer-2 security and cross-chain vulnerabilities. Our findings emphasize the need for rigorous testing frameworks and standardized security protocols to mitigate risks in decentralized applications

Keywords: Blockchain, Smart Contracts, Security Vulnerabilities, Formal Verification, Decentralized Applications