Bookstack · Bookstack · CVE-2020-5256
**Name of the Vulnerable Software and Affected Versions**
BookStack versions prior to 0.25.5
**Description**
A user could upload PHP files through image upload functions, which would allow them to execute code on the host system remotely. They would then have the permissions of the PHP process. This most impacts scenarios where non-trusted users are given permission to upload images in any area of the application.
**Recommendations**
For BookStack versions prior to 0.25.5, upgrade to at least version 0.25.5 to avoid this issue.
As a temporary workaround, consider using the local secure image storage option, or use s3 or a similar compatible service.
Prevent direct execution of any `php` files, apart from the `public/index.php` file, through web-server configuration.