Craft CMS is a content management system (CMS). From version 4.0.0-RC1 to before version 4.17.8 and from version 5.0.0-RC1 to before version 5.9.14, an unauthenticated user can call assets/generate-transform with a private assetId, receive a valid transform URL, and fetch transformed image bytes. The endpoint is anonymous and does not enforce per-asset authorization before returning the transform URL. This issue has been patched in versions 4.17.8 and 5.9.14.

Affected: Packagist: craftcms/cms

### Summary

An unauthenticated user can call `assets/generate-transform` with a private `assetId`, receive a valid transform URL, and fetch transformed image bytes.

The endpoint is anonymous and does not enforce per-asset authorization before returning the transform URL.

### Details

Root cause: - Anonymous endpoint accepts user-controlled asset reference. - It creates and returns a transform URL for that asset without checking access rights. - If the transform output is reachable, guest users can read content derived from private assets.

Who is impacted:

- Installations where private source assets can be transformed and transform URLs are reachable.

Security consequence:

- Anonymous users can obtain content derived from private assets without authentication.

### Resources

https://github.com/craftcms/cms/commit/7290d91639e