This issue was addressed with improved checks. This issue is fixed in macOS Catalina 10.15.1, Security Update 2019-001, and Security Update 2019-006, macOS Catalina 10.15. Parsing a maliciously crafted text file may lead to disclosure of user information.
https://www.paulosyibelo.com/2021/04/this-man-thought-opening-txt-file-is.html