Thanks to BrowserUK for pointing out the priority implications of the ordering of items in PATHEXT.

It leads to to another thought -- maybe somebody has already done it. There is a tremendous amount of information on this site and that other one, LinuxQuestions, and several other similar places. But that info is extremely hard to access. Is there something like a Wiki of info on Windows, Perl, or a thousand other computer issues? I have a huge library of books collected over 30-some years of programming -- and that info is also just about as hard to get to. There must be a better answer.

The MS tech info site is a good start, but they only tell you what they want you to know. Not much scurrilous poop there. Here's one of my peeves: In older Win OSs, I habitually used DownArrow to redo the last command or bring it up for editing. Now, I get something from the past that some MS programmer thought I would like. I've heard there are ways around that, but I have not found any more than that.

A better example is the Unix/Linux HOWTO collection. An excellent body of reference material. Of course, it needs to be kept up to date. A Wiki is good that way.

but it might also in some cases be a security issue,

No more (or less) so that the PATH variable; and it is a well known situation that has been around forever.

But, like the PATH, if the miscreant has the ability (access) to change the environment variable to cause you to run the wrong executable; then they also have the ability to replace the original executable with the (renamed) one they want you to run; or set up a shell alias to cause it to be run.

Some things are worth worrying about, and (assuming basic precautions), some things are not.