I found a directory traversal in `actionpack-page_caching`.
Some code may lead to RCE.
https://github.com/rails/actionpack-page_caching/blob/master/lib/action_controller/caching/pages.rb#L143
```ruby
def cache_file(path, extension)
if path.empty? || path =~ %r{\A/+\z}
name = "/index"…