bug#43302: password shows up in shell buffer (27.1)

[Nicholas Drozd <nicholasdrozd@gmail.com>]

The password input starring in shell mode seems to have changed in 27
from 26 to become more lax. Here is a small shell script:

#+begin_src shell
echo "Password:"
read -sr password
#+end_src

In 26, it looks like this when I run it:

#+begin_quote
$ bash password.sh
Password:
$
#+end_quote

The password is input starred into the minibuffer, not in the shell
buffer itself.

In 27, it looks like this:

#+begin_src
$ bash password.sh
Password:
asdf
$
#+end_src

The password (=asdf=) gets input directly into the shell buffer, unstarred.

I have tried on both Linux and Mac.

This may be related to
https://lists.gnu.org/archive/html/bug-gnu-emacs/2020-09/msg00028.html