PrivateBin's template-switching feature allows arbitrary local file inclusion through path traversal

Vulnerability Description

PrivateBin is an online pastebin where the server has zero knowledge of pasted data. Starting in version 1.7.7 and prior to version 2.0.3, an unauthenticated Local File Inclusion exists in the template-switching feature. If `templateselection` is enabled in the configuration, the server trusts the `template` cookie and includes the referenced PHP file. An attacker can read sensitive data or, if they manage to drop a PHP file elsewhere, gain remote code execution. The constructed path of the template file is checked for existence, then included. For PrivateBin project files this does not leak any secrets due to data files being created with PHP code that prevents execution, but if a configuration file without that line got created or the visitor figures out the relative path to a PHP script that directly performs an action without appropriate privilege checking, those might execute or leak information. The issue has been patched in version 2.0.3. As a workaround, set `templateselection = false` (which is the default) in `cfg/conf.php` or remove it entirely

References

• https://github.com/PrivateBin/PrivateBin/security/advisories/GHSA-g2j9-g8r5-rg82
• https://github.com/PrivateBin/PrivateBin/commit/4434dbf73ac53217fda0f90d8cf9b6110f8acc4f