Privilege escalation

Privilege escalation is the act of exploiting a bug in an application to gain access to resources which normally would have been protected from an application or user. The result is that the application performs actions with a higher security context than intended by the application developer or system administrator.

Privilege escalation examples

Cross Zone Scripting, is a type of privilege escalation attacks.
A Microsoft Windows Service is usually configured run as Local System command. A vulnerability, e.g. buffer overflow or Shell Injection may be used to execute arbitrary code with privilege elevated to Local System.
In Unix it is not uncommon to have a few commands with suid root. A vulnerability, e.g. Buffer Overflow or Shell Injection may be used to execute arbitrary code with privilege elevated to root.