SSH into your router and then do the following:
1.cd /
2.mkdir firmware
3.cd firmware
4.wget http://download.gl-inet.com/download/RM520GL-modem_firmware/RM520NGLAAR03A03M4G_01.201.01.201.zip
5.unzip RM520NGLAAR03A03M4G_01.201.01.201.zip -d RM520NGLAAR03A03M4G_01.201.01.201
6.QFirehose -f RM520NGLAAR03A03M4G_01.201.01.201
7.reboot