Vulnerable dependencies are a major problem in modern software development. As software projects depend on multiple external dependencies, developers struggle to constantly track and check for corresponding security vulnerabilities that affect their project dependencies. To help mitigate this issue, Dependabot has been created, a bot that issues pull-requests to automatically update vulnerable dependencies. However, little is known about the degree to which developers adopt Dependabot to help them update vulnerable dependencies. In this paper, we investigate 2,904 JavaScript open-source GitHub projects that subscribed to Dependabot. Our results show that the vast majority (65.42%) of the created security-related pull-requests are accepted, often merged within a day. Through manual analysis, we identify 7 main reasons for Dependabot security pull-requests not being merged, mostly related to concurrent modifications of the affected dependencies rather than Dependabot failures. Interestingly, only 3.2% of the manually examined pull-requests suffered from build breakages. Finally, we model the time it takes to merge a Dependabot security pull-request using characteristics from projects, the fixed vulnerabilities and issued pull requests. Our model reveals 5 significant features to explain merge times, e.g., projects with relevant experience with Dependabot security pull-requests are most likely associated with rapid merges. Surprisingly, the severity of the dependency vulnerability and the potential risk of breaking changes are not strongly associated with the merge time. To the best of our knowledge, this study is the first to evaluate how developers receive Dependabot’s security contributions. Our findings indicate that Dependabot provides an effective platform for increasing awareness of dependency vulnerabilities and helps developers mitigate vulnerability threats in JavaScript projects.