However, the TR-069 client ( cwmpd ) listens on both WAN and LAN on port 7547. That’s the real concern. If you don’t disable remote management, cwmpd has been vulnerable in the past (CVE-2017-3187-style issues). D-Link patched this in v1.03, but worth checking.
However, as with any complex electronic device, the DSL-X1852E's performance and features were not set in stone. The true potential of the device lay in its firmware, the software that controlled its operations. The initial firmware, version 1.0.0, was a good starting point, but it had its limitations. dsl-x1852e firmware