Description of problem:

Since upgrading to 9.0, when logged in as user1 but firefox running under user2 who has display permission (in order to have access to a different set of files), firefox displays OK but right-clicks cause it to hang and trying to use the drop-down menus causes it to hang.

Version-Release number of selected component (if applicable):

firefox-91.12.0-2.el9_0.x86_64.rpm

How reproducible: Always

Steps to Reproduce:
1. Login as user1 using x11 and Gnome-classic.

2. Give user2 permission to display by

xhost +si:localuser:rfsnet

3. su - user2
(appropriate password)

4. firefox &

5. Right-click on any of the links on the default home page, OR hit alt-B to get a drop-down menu to appear (OR alt-anything else).

Actual results:

Firefox becomes unresponsive, and a window asking whether you want to force-quit appears. Before you can get firefox to run again, you need to not only say force-quit, but also look for the process using ps and explicitly kill it. On occasion the whole system also hangs, but usually it doesn't.

Expected results:

Appropriate menu appears.

Additional info:

a. The problem persists if one downgrades firefox e.g. to firefox-91.4.0-1.el8_5.x86_64.rpm without changing anything else; this is notable because this latter version worked fine under 8.5 .

b. Under 9.0 okular, gnome-terminal, and other apps run fine under user2, including drop-down menus and right-clicks.

c. Making selinux permissive doesn't improve matters.

It's very hard to be sure that I'm filing this bug under the correct package, as I suspect that this version of firefox would run fine under 8.5 or 8.6 if one could install it; the reason for choosing to file it under firefox is point (b) above.