[alnsn]

It depends on how much effort you put in making sure your parser is robust. I ran AFL tests for several days trying to find bugs in Lua parser but AFL kept discovering a way to load a binary chunk. After that, it didn't take to crash on a malformed binary chunk. Priv separation is a good idea even if you trust your parser.

[DominikD]

This is true for any piece of code but you wouldn't say that it about, say, httpd (oh, priv separation isn't needed if you put enough effort in making sure your protocol implementation is robust). Plus: file (well, magic) is a configurable parser.