GL.iNet XE3000 Language Update ui.update_langs code injection

A security flaw has been discovered in GL.iNet A1300, AX1800, AXT1800, BE1400, BE3600, BE6500, BE9300, BE10000, E5800, MT2500, MT3000, MT3600BE, MT5000, MT6000, X2000, X3000 and XE3000 up to 4.8.x. Affected by this issue is the function ui.update_langs of the component Language Update. Performing a manipulation of the argument hour/min/week results in code injection. The attack can be initiated remotely. The vendor explains: "After our investigation, we have confirmed that the vulnerability described (...) does indeed exist."