You could also just steganographically encode it. You have the entire URL after the domain name to encode leaked data into. LLMs can do things like base-64 encoding no sweat. Encode some into the 'ID' in the path, some into the capitalization, some into the 'filename', some into the directories, some into the 'arguments', and a perfectly innocuous-looking functional URL now leaks hundreds of bytes of PII per request.