1. A computer-implemented method for installing a browser extension in a browser application, the method comprising: receiving, in a main process of the browser application running on a computing system, a browser extension installation package for installation in the browser application, the browser extension installation package including a header and a compressed, archived file, the compressed archived file containing a plurality of constituent files of the browser extension; placing the browser extension installation package in a temporary directory; launching a sandboxed sub-process of the browser application, the sandboxed sub-process having access to the temporary directory; in the sandboxed sub-process: unpacking the compressed, archived file into the plurality of constituent files of the browser extension; and respectively performing one of transcoding and recoding of at least one of the plurality of constituent files, wherein transcoded and recoded files replace their corresponding original constituent; files, wherein the sandboxed sub-process is restricted to accessing only resources of the computing system allocated to it by the main browser process; after the respective transcoding and recoding, passing the constituent files back to the main browser process; and in the main process of the browser application, installing the browser extension to the browser application using the passed back constituent files.