Bypass vulnerability in Active Storage

There is a vulnerability in Active Storage. This vulnerability has been
assigned the CVE identifier CVE-2018-16477.

Versions Affected: >= 5.2.0
Not affected: < 5.2.0
Fixed Versions: 5.2.1.1

Impact

Signed download URLs generated by ActiveStorage for Google Cloud Storage
service and Disk service include content-disposition and content-type
parameters that an attacker can modify. This can be used to upload specially
crafted HTML files and have them served and executed inline. Combined with
other techniques such as cookie bombing and specially crafted AppCache manifests,
an attacker can gain access to private signed URLs within a specific storage path.

Vulnerable apps are those using either GCS or the Disk service in production.
Other storage services such as S3 or Azure aren’t affected.

All users running an affected release should either upgrade or use one of the
workarounds immediately. For those using GCS, it’s also recommended to run the
following to update existing blobs:

ActiveStorage::Blob.find_each do |blob|
  blob.send :update_service_metadata
end