Abstract: The following disclosure shows a window security system. The window security system comprises a grate or security bar assembly that is hinged to the outside of a window and includes louvres attached to the grate for protecting against the elements and in particular, sunlight. The grate is hinged to the window at one side, while on the other side, it is secured by means of a latch comprising a pointed latch pin which is engaged by a pair of jaws that are pivotally actuated by a toggle member. The toggle member can be actuated by a solenoid or by a hand operated cable or other assembly attached thereto. The solenoid can be either pushbutton operated or operated by means of a smoke detector. The entire assembly, including the grate and the louvres are opened at the time of the smoke detector detecting combustion to protect against entrapping occupants in the building.