This port is released for forwarding in the FRITZ!Box when you enable MyFRITZ! sharing in FRITZ!App Cam.
Port 8080 is preconfigured. You can also release a different port for forwarding:
If MyFRITZ! sharing is already enabled, the port is changed automatically in the FRITZ!Box.
The port forwarding settings are listed in the FRITZ!Box user interface under Internet > Permit Access.