An issue was discovered on Foscam C2 devices with System Firmware 1.11.1.8 and Application Firmware 2.72.1.32, and Opticam i5 devices with System Firmware 1.5.2.11 and Application Firmware 2.21.1.128. The firewall feature makes it easier for remote attackers to ascertain credentials and firewall rules because invalid credentials lead to error -2, whereas rule-based blocking leads to error -8.