Improper Limitation of a Pathname to a Restricted Directory ('Path Traversal')
Directory traversal vulnerability in admin/skins.php for @lex Guestbook 4.0.2 and earlier allows remote attackers to create files in arbitrary directories via ".." sequences in the (1) aj_skin and (2) skin_edit parameters. NOTE: this can be leveraged for file inclusion by creating a skin file in the lang directory, then referencing that file via the lang parameter to index.php, which passes a sanity check in livre_include.php.
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.