Thymeleaf through 3.1.1.RELEASE, as used in spring-boot-admin (aka Spring Boot Admin) through 3.1.1 and other products, allows sandbox bypass via crafted HTML. This may be relevant for SSTI (Server Side Template Injection) and code execution in spring-boot-admin if MailNotifier is enabled and there is write access to environment variables via the UI.

Spring boot admins is an open source administrative user interface for management of spring boot applications. All users who run Spring Boot Admin Server, having enabled Notifiers (e.g. Teams-Notifier) and write access to environment variables via UI are affected. Users are advised to upgrade to the most recent releases of Spring Boot Admin 2.6.10 and 2.7.8 to resolve this issue. Users unable to upgrade may disable any notifier or disable write access (POST request) on `/env` actuator endpoint.