Pop the rear window and run some rope or bungees around the frame and secure it under the rear somewhere.
You should be fine as long as your not driving long distance or on the highway.
2014 - Altitude - Billet Silver
5k vled led fogs, 15% tint, Mopar Slush Mats & Cargo Mat
Ready for install: Overland Mesh Inserts, DDM 5k HID Kit, JL 250/1
Next: Gorilla Blk 20pc Lock Kit, 1.5" Bora Spacers, JL Stealth Box