FreeScout's Mass Assignment in Mailbox Connection Settings Enables Silent Email Exfiltration

FreeScout is a free self-hosted help desk and shared mailbox. Versions prior to 1.8.213 have a mass assignment vulnerability in the mailbox connection settings endpoints of FreeScout (connectionIncomingSave() at app/Http/Controllers/MailboxesController.php:468 and connectionOutgoingSave() at line 398). Both methods pass $request->all() directly to $mailbox->fill() without any field allowlisting, allowing an authenticated admin to overwrite any of the 32 fields in the Mailbox model's $fillable array -- including security-critical fields that do not belong to the connection settings form, such as auto_bcc, out_server, out_password, signature, auto_reply_enabled, and auto_reply_message. Validation in connectionIncomingSave() is entirely commented out, and the validator in connectionOutgoingSave() only checks value formats for SMTP fields without stripping extra parameters. An authenticated admin user can exploit this by appending hidden parameters (e.g., auto_bcc=attacker@evil.com) to a legitimate connection settings save request. Because the auto_bcc field is not displayed on the connection settings form (it only appears on the general mailbox settings page), the injection is invisible to other administrators reviewing connection settings. Once set, every outgoing email from the affected mailbox is silently BCC'd to the attacker via the SendReplyToCustomer job. The same mechanism allows redirecting outgoing SMTP through an attacker-controlled s…