CB 2.12.0 System Plugin causes HTTP 403 on PHP 8.3 (works on PHP 8.2)

Hello,I am encountering a reproducible issue with Community Builder 2.12.0 on Joomla 5.4.8 when switching PHP from 8.2 to 8.3.Environment:

• Joomla 5.4.8
• Community Builder 2.12.0
• PHP 8.2.33: working
• PHP 8.3.33: issue occurs
• MySQL 8.4
• Apache behind Nginx reverse proxy
• CB System plugin enabled
• CB login menu item is publicly accessible / Guest access

Problem:
Under PHP 8.3, the Community Builder login page returns HTTP 403 with the Joomla message:“You are not authorised to view this resource.”The same site works normally under PHP 8.2.I isolated the issue as follows:

1. PHP 8.3 + CB System plugin enabled:
   /fr/connexion.html
   -> HTTP 403
2. PHP 8.3 + CB System plugin disabled:
   /fr/connexion.html
   -> HTTP 200
3. Native Joomla com_users login also works under PHP 8.3 when the CB System plugin is disabled.
4. Re-enabling the CB System plugin immediately makes the direct CB login page return HTTP 403 again.
5. Setting the CB System plugin parameter:
   rewrite_urls = 0
   does not resolve the issue.
6. Setting:
   redirect_urls = 0
   also does not resolve the refusal.
7. I also tested the Joomla/Apache container directly, bypassing the public Nginx Basic Authentication layer. The CB login page still returns:
   HTTP/1.0 403 Forbidden

So the 403 is generated inside Joomla/CB, not by the Nginx reverse proxy.The relevant CB System plugin parameters were originally:redirect_urls = 1
rewrite_urls = 1
verify_consent = 0The Joomla Guest user group and menu ACLs appear correct. The CB login menu item is assigned to Guest access, and the same configuration works under PHP 8.2.Could you please advise whether there is a known PHP 8.3 issue in the CB 2.12.0 System plugin, or suggest which part of the plugin/API should be investigated next?I can provide additional logs or perform targeted diagnostic tests if needed.Thank you.

CBs login page only throws a 403 if you've an HTTPS mismatch (e.g. HTTP POST) and "Encrypt Login Form" is enabled in your CB Login Module. Try turning that off in your CB Login Module and see if your issue persists.