I applied the security fix that I made for the EPiServer CMS 6 R2 version of the Language File Editor tool to the EPiServer 7 version that Hannu Hartikainen made earlier. Also did some code refactoring and removed the possibility for web administrators to create their own language files, as well as deleting existing ones; these were a source for potential headache. Code available at GitHub.
Original post here: Allowing web administrators to dynamically update EPiServer language files.
