Web of Things (WoT) technology standardizes the integration of various IoT devices deployed in daily environments, promoting the capability of applications to automatically sense and regulate the physical environment. Meanwhile, the complex nature of such a ubiquitous software system, where heterogeneous applications, user activities, and environment states collectively influence device behaviors, poses risks of unexpected or even hazardous safety and security violations caused by improper device operations. Existing works on WoT violation identification primarily focus on the sole analysis of software applications, however, lacking consideration of the multi-source violations stemming from the human-cyber-physical ternary spaces, as well as the intricate interplay between environment and devices. Furthermore, the investigation into users’ preferences for violation resolution remains unexplored. To address these limitations, we introduce EnvGuard, an environment-centric approach for customizing safety and security properties, identifying violations, and executing resolutions in the WoT environment. Our evaluation in two real-world WoT systems shows that EnvGuard outperforms previous state-of-the-art works, and confirms its usability, effectiveness, and runtime efficiency.