Certain GL.iNet devices with 4.x firmware allow authentication bypass (resulting in administrative control of the device) via a username that is both a valid SQL statement and a valid regular expression. For example, this affects version 4.3.7 on GL-MT3000 GL-AR300M GL-B1300 GL-AX1800 GL-AR750S GL-MT2500 GL-AXT1800 GL-X3000 and GL-SFT1200.