LuaSandbox provides a sandboxed environment which differs in some ways from standard Lua 5.1.
dofile(), loadfile(), and the io package, as they allow direct filesystem access. If needed, filesystem access should be done via PHP callbacks.
The package package, including require() and module(), as it depends heavily on direct filesystem access. A pure-Lua rewrite such as that used in the MediaWiki Scribunto extension may be used instead.
load() and loadstring(), to allow for static analysis of Lua code.
print(), since it outputs to standard output. If needed, output should be done via PHP callbacks.
Most of the os package, as it allows manipulation of the process and executing of other processes.
os.clock(), os.date(), os.difftime(), and os.time() remain available.
Most of the debug package, as it allows manipulation of Lua state and metadata in ways that can break sandboxing.
debug.traceback() remains available.
string.dump(), as it may expose internal data.
collectgarbage(), gcinfo(), and the coroutine package have not been reviewed for security.
pcall() and xpcall() cannot catch certain errors, particularly timeout errors.
tostring() does not include pointer addresses.
string.match() has been patched to limit the recursion depth and to periodically check for a timeout.
math.random() and math.randomseed() are replaced with versions that don't share state with PHP's rand().
The Lua 5.2 __pairs and __ipairs metamethods are supported by pairs() and ipairs().