The present disclosure relates to computer-implemented methods, software, and systems for providing extension application mechanisms. Memory is allocated for a virtual environment to run in an address space of an application that is to be extended with extension logic in a secure manner. The virtual environment is configured for execution of commands related to an extension functionality of the application. A virtual processor for an execution of a command of the commands is initialized at the virtual environment. The virtual processor is operable to manage one or more guest operating systems (OS). A first guest OS is loaded at the allocated memory and application logic of the extension functionality is copied into the allocated memory. The virtual environment is started to execute the first guest OS and the application logic of the extension functionality in relation to associated data of the application in the allocated memory.