This is a terrible description of the lethal trifecta, it lists 3 things but they are not the trifecta. The trifecta happens to be contained in the things listed in this (and other) examples but it's stated as if the trifecta is listed here, when it is not.
The trifecta is: access to your private data, exposure to untrusted content, and the ability to externally communicate. Web search as tool for an LLM agent is both exposure to untrusted content and the ability to externally communicate.