Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Directory traversal vulnerability in the get_lang function in global.php in Quicksilver Forums 1.4.2 and earlier, as used in QSF Portal before 1.4.5, when running on Windows, allows remote attackers to include and execute arbitrary local files via a "\" (backslash) in the lang parameter to index.php, which bypasses a protection mechanism that only checks for "/" (forward slash), as demonstrated by uploading and including PHP code in an avatar file.
CWE-22 - Path Traversal
Path traversal (or directory traversal), is a vulnerability that allows malicious users to traverse the server's root directory, gaining access to arbitrary files and folders such as application code & data, back-end credentials, and sensitive operating system files. In the worst-case scenario, an attacker could potentially execute arbitrary files on the server, resulting in a denial of service attack. Such an exploit may severely impact the integrity, confidentiality, and availability of an application.