The original “secret string” was url encoded, which when decoded was a binary string that read: .dnuof ecnedivE !EGASSEM TNEGRU !ffo pord rotartlifni kcehc

When reversed it reads: check infiltrator drop off! URGENT MESSAGE! Evidence found.

Update www.coldfusing.com/infiltrator reads:
MEMO

Subject: Surveillance subject

Managed to find evidence as per request.

Check securemail immediately…

Infiltrator xxx