Explore the security implications of speculative execution in CPUs through this 23-minute conference talk presented at the Association for Computing Machinery (ACM). Delve into the optimization technique of speculative execution, which predicts branch instruction outcomes to enhance pipeline efficiency. Examine the previously understudied security risks associated with this long-standing CPU feature. Learn about return stack buffers, proof of concept demonstrations, execution contexts, and potential countermeasures. Gain insights into a second attack vector and additional protective measures. Conclude with a comprehensive understanding of the ret2spec vulnerability and its significance in modern processor architecture.