This means two things
1) the owner of that site might spread malware infecting many many people.
2) the ISP also might do that.
Firefox Quantum version:
The URL: hxxp://ciscobinary.openh264.org/openh264-linux64-0410d336bb748149a4f560eb6108090f078254b1.zip
The zip contains these two files:
The info file:
Description: GMP Plugin for OpenH264.
APIs: encode-video[h264], decode-video[h264]
So there is a remote codec loading system that is unsigned and unencrypted, I think is good to be aware of it.