backpack/crud: SingleBase64Image accepts any base64 payload behind a `data:image` prefix — SVG-with-script lands on the public disk

backpack/crud provides Create, Read, Update & Delete (CRUD) functions for Backpack, a collection of Laravel packages that help users build custom administration panels. From 6.0.0 until 6.8.14 and 7.0.37, the src/app/Library/Uploaders/SingleBase64Image.php methods SingleBase64Image::uploadFiles and SingleBase64Image::uploadRepeatableFiles, used by image fields through withFiles(), accept any data URI beginning with data:image without validating the declared MIME subtype or decoded bytes, while src/app/Library/Uploaders/Support/FileNameGenerator.php method FileNameGenerator::getExtensionFromFile applies mime_content_type() to the data URI instead of the decoded content. An authenticated administrator can therefore store arbitrary file content under an extensionless filename on the configured disk, which can cause stored cross-site scripting or other unintended behavior when the file is served and accessed. This issue is fixed in version 7.0.38 and 6.8.14.