An insecure deserialization vulnerability exists in the download.php script of the to3k Twittodon application through commit b1c58a7d1dc664b38deb486ca290779621342c0b (2023-02-28). The 'obj' parameter receives base64-encoded data that is passed directly to the unserialize() function without validation. This allows a remote, unauthenticated attacker to inject arbitrary PHP objects, leading to a denial of service.