ack 2.00 through 2.11_02 allows remote attackers to execute arbitrary code via a (1) --pager, (2) --regex, or (3) --output option in a .ackrc file in a directory to be searched.
Improper Control of Generation of Code The product constructs all or part of a code segment using externally-influenced input from an upstream component, but it does not neutralize or incorrectly neutralizes special elements that could modify the syntax or behavior of the intended code segment.