A weapon comprising: a firing pin; a trigger; a safety comprising a movable sear between a safe position that prevents the firing pin from being released and a firing position that allows the firing pin to be released when the trigger is pulled; and a device for securing the weapon or a trigger mechanism housing comprising the device, wherein the device comprises: a safety body adapted to contact the sear, and an actuating element movable between: a first position in which the actuating element is located into a path of movement of the safety body in a direction of movement of the safety body, and a second position in which the actuating element is located out of the path of movement of the safety body in the direction of movement of the safety body; characterized in that the actuating element and the safety body are adapted to make the device configurable between at least: a firing state in which the actuating element is in the first position that does not allow the movement of the safety body in the direction of movement, causing the sear to slide through the safety body and, in this way, is able to release the firing pin only when the safety is in the firing position, thus allowing a user to shoot; and a safe state in which the actuating element is in the second position that allows the movement of the safety body in the direction of movement, causing the sear not to slide through the safety body and, in this way, is not able to release the firing pin and not to allow the user to shoot neither when the safety is in the firing position nor when the safety is in the safe position. a firing pin; a trigger; a safety comprising a movable sear between a safe position that prevents the firing pin from being released and a firing position that allows the firing pin to be released when the trigger is pulled; and a device for securing the weapon or a trigger mechanism housing comprising the device, wherein the device comprises: a safety body adapted to contact the sear, and an actuating element movable between: a first position in which the actuating element is located into a path of movement of the safety body in a direction of movement of the safety body, and a second position in which the actuating element is located out of the path of movement of the safety body in the direction of movement of the safety body; characterized in that the actuating element and the safety body are adapted to make the device configurable between at least: a firing state in which the actuating element is in the first position that does not allow the movement of the safety body in the direction of movement, causing the sear to slide through the safety body and, in this way, is able to release the firing pin only when the safety is in the firing position, thus allowing a user to shoot; and a safe state in which the actuating element is in the second position that allows the movement of the safety body in the direction of movement, causing the sear not to slide through the safety body and, in this way, is not able to release the firing pin and not to allow the user to shoot neither when the safety is in the firing position nor when the safety is in the safe position. a safety body adapted to contact the sear, and an actuating element movable between: a first position in which the actuating element is located into a path of movement of the safety body in a direction of movement of the safety body, and a second position in which the actuating element is located out of the path of movement of the safety body in the direction of movement of the safety body; characterized in that the actuating element and the safety body are adapted to make the device configurable between at least: a firing state in which the actuating element is in the first position that does not allow the movement of the safety body in the direction of movement, causing the sear to slide through the safety body and, in this way, is able to release the firing pin only when the safety is in the firing position, thus allowing a user to shoot; and a safe state in which the actuating element is in the second position that allows the movement of the safety body in the direction of movement, causing the sear not to slide through the safety body and, in this way, is not able to release the firing pin and not to allow the user to shoot neither when the safety is in the firing position nor when the safety is in the safe position. a firing state in which the actuating element is in the first position that does not allow the movement of the safety body in the direction of movement, causing the sear to slide through the safety body and, in this way, is able to release the firing pin only when the safety is in the firing position, thus allowing a user to shoot; and a safe state in which the actuating element is in the second position that allows the movement of the safety body in the direction of movement, causing the sear not to slide through the safety body and, in this way, is not able to release the firing pin and not to allow the user to shoot neither when the safety is in the firing position nor when the safety is in the safe position.