Google's John Mueller said Google may discover and index URLs it finds in form action attributes, just like it does when it finds URLs in simple text files. Again, these are not normal HTML hyperlinks but URLs listed in files.
The question was "Does Google(bot) follow links inside a form action attribute?" John said "usually not, though we might recognize something as a URL and just check to see if it works. Kinda like when you have a URL in a text file."
Usually not, though we might recognize something as a URL and just check to see if it works. Kinda like when you have a URL in a text file.
— 🍌 John 🍌 (@JohnMu) February 18, 2021
So it might be rare but Google does have the ability to read these URLs and discover them that way.
Forum discussion at Twitter.