Livewire Remote Code Execution (RCE) on File Uploads

Livewire is a full-stack framework for Laravel that allows for dynamic UI components without leaving PHP. In livewire/livewire prior to `2.12.7` and `v3.5.2`, the file extension of an uploaded file is guessed based on the MIME type. As a result, the actual file extension from the file name is not validated. An attacker can therefore bypass the validation by uploading a file with a valid MIME type (e.g., `image/png`) and a “.php” file extension. If the following criteria are met, the attacker can carry out an RCE attack: 1. Filename is composed of the original file name using `$file->getClientOriginalName()`. 2. Files stored directly on your server in a public storage disk. 3. Webserver is configured to execute “.php” files. This issue has been addressed in release versions `2.12.7` and `3.5.2`. All users are advised to upgrade. There are no known workarounds for this vulnerability.