security - Runtime stack should not be executable -

i'm reading security in embedded systems,and came on statement: "the web browser’s runtime stack should not executable.". aware of stack is, , how works, i'm having hard time understanding not being executable means. mean should not able change stack @ runtime, or something?

for von neumann architecture (the common today), programs , data stored in same memory. so, there has distionction of program , data. moreover, without control of executed, many programs can malicious jobs. 1 way prevent malicious programs doing bad things is, @ execution of program, load code in read only, executable memory region , use stack writable memory region cannot executed.

there thing called program counter points current instruction being executed. program may change value point stack , execute malitious instructions there, can recieved on network, example, givin access unauthorized person machine.

also, in linux operating system, there permission system allows specify whether file can executed or not , persons.

this thread: linux process memory scheme has pretty explicit image of how memory of process organised. text section, contains code, executabile (this means program counter can point memory cell in region).