Blanks removed from URL params

Apologies if this topic appears twice. I got disconnected as I was sending the first time, and I cannot see the post.

I have WordPress installed on my own Linux system, and one of the pages is actually designed as a landing page for an application. The page is reached through:
http://mywpinstall.com/myapp/

Inside that page, I only have the following:
<?php
include myscript.php
?>

myscript.php displays a form to be filled, and the form’s action is http://mywpinstall.com/myapp/

This has been working for several months (I have the Execute PHP plugin installed). With the past few WordPress updates, I started noticing strange behavior, and now I noticed that the spaces are removed from the URL params. For example, if the form is supposed to send the following:

http://mywpinstall.com/myapp/?question=Where+are+the+spaces&submit=Submit

In the browser bar, I see:

http://mywpinstall.com/myapp/?question=Wherearethespaces&submit=Submit

Any ideas? I have a number of applications and this is messing up everything I’m storing in my database, etc.