An assumption made by many virtual terminals is that the input and output stream are trusted. For instance `cat file.txt` in a terminal result in your terminal being sent escape sequences that will change how your terminal functions well after you quit cat.

I've always wanted a virtual terminal that had a terminal state stack, when you run a command or open a program, all the changes to the terminal are pushed on the top of terminal stack. When I quit the program or the command stops, the state is popped. It seems like it would be very difficult to implement such a thing in the current terminal framework because as far as I can tell, they do not understand when a command starts or stops. Then again the effectiveness of virtual terminals over the last 5 or so decades is likely because of this simplicity and its corresponding flexibility.

It seems to have a hand-written ad hoc parser, handling untrusted input. A very rich source of exploits. (Luckily it's at least using a memory safe language so what you can do is likely limited to DoSing yourself or using up all memory as in this case.)