Arbitrary file read and write via folder traversal

Path traversal in ClipBucket V5 5.5.2 - #146 and earlier allows remote authenticated users to read and write arbitrary files. The template editor joins untrusted folder and file query parameters into a filesystem path and performs reads or writes without verifying that the resolved path remains beneath the selected template directory. Administrator privileges are required, and modification is limited to files writable by the web-server process.