This is just too weird. Now another site I haven't touched in terms of CB "features" for probably over a year no longer allows anyone to log in on the front end. I can't even log into my super admin account on the front end, yet I can on the back end. Captcha seems to work since after a few failed attempts I get the picture test. This site has no auto actions that trigger off a user logging in. And again, I haven't worked on this site in months and haven't messed with any CB configuration in probably over a year. This just started happening out of the blue. I truly would not even have known about it had one of my users (neighbors) inform me that he can't login. So I tried and neither can I...using any of my own accounts. But fortunately, back end login works fine.

I have tried setting the message level to Development and enabled Joomla debug, but that yields nothing. It just won't log me in.

Stuck. Really. Stuck. No idea where to look.

Joomla 3.9.24, CB 2.5.0+build.2021.02.01.21.20.37.ae3d43f4e
(Note: was occurring with CB 2.5.0 also)

Bruce

Definitely not the same as the other site. This one has very few auto actions and all of them are triggered off the user saving their profile, which obviously comes long after logging in. I suspect a recent update of some extension is causing the issue. However, this site is pretty simple. There is nothing "fancy" going on with it. It doesn't even have that many extensions installed.

The most recent updates within the last month are (in order newest to oldest):

• CB (incl. all professional add-ons)
• JCE Pro
• Akeeba Backup
• Admin Tools
• Regular Labs Tooltips
• Regular Labs Components Anywhere
• googl Shortener (I don't know what installed this)
• JEvents
• Joomla (3.9.24)
• Regular Labs Better Preview

All of these have been disabled individually (except for any CB extension) and in each case doing so made no difference. Both Akeeba and Admin Tools have been fully uninstalled and, again, doing so made no difference. I know logins were working when J! 3.9.24 was released and updated on the site.

Something else notable: I put the site in offline mode and I can log into the front just fine as super-admin.

So although CB may not be a "time bomb", it certainly appears something is. And because the site uses the CB login module and I have only NOT disabled CB extensions, it seemed like the right place to start.

Found the problem using an external site auditing service. Turns out the $live_site variable in configuration.php was set to the actual site URL. Setting it to an empty string resolved both the login and "Unknown Joomla..." issues. I am quite certain that setting was carried over from the J! 1.5 days or at least the very early 3.x days. Anyway, due to that being the issue, I suspect it was actually the Joomla update to 3.9.24 that caused the issue.

Anyway, problem solved!