: Manufacturers release security patches regularly. If your camera is "legacy" and no longer gets updates, it’s time to replace it. Disable UPnP

: This part indicates you're also interested in content that has "webcam" in the title of the webpage. This narrows down your search to web pages that discuss webcams, possibly in the context of multiple webcams, streaming, or using webcams in HTML for various applications.

Why does this specific combination exist? Why aren't modern cameras like Ring or Nest appearing in these results?

: Filters results for web pages that contain "/multi.html" in their URL. This specific filename is often associated with the user interface of older or generic IP camera software.

: This feature often automatically opens ports on your router to make the camera accessible from the internet, unknowingly exposing the login page to search engine crawlers.

So, the entire query inurl:multi html intitle:webcam is searching for web pages that have "multi" and "html" somewhere in their URL and "webcam" in the title of the page. This could potentially lead to pages that offer multiple webcam streams, are related to multi-camera setups, or offer information on how to create or embed webcam feeds using HTML.