Recently, Check Point Research released a white paper titled “The Obvious, the Normal, and the Advanced: A Comprehensive Analysis of Outlook Attack Vectors”, detailing various attack vectors on Outlook to help the industry understand the security risks the popular Outlook app may bring into organizations. As mentioned in the paper, we discovered an interesting security issue in Outlook when the app handles specific hyperlinks. In this blog post, we will share our research on the issue with the security community and help defend against it. We will also highlight the broader impact of this bug in other software.