What is x-speed-cache-key? What is its purpose? Our drupal site was pentested.  The pentest report labeled an action involving the header X-Speed-Cache-Key as a security concern.

The finding stated:


  Arbitrary parameters supplied to the query string are returned to the user unencoded in the X-Speed-Cache-Key response header.


I'm not familiar with caching or with the header x-speed-cache-key. For a Drupal site functionality should the x-speed-cache-key function as stated in the finding? Is this a valid security concern for Drupal? Is the x-speed-cache-key header provided by a module, or is it a part of Drupal core?
Best I can find on Google is that this header (and its companion header 'X-Speed-Cache') are added by a web server level module called "Speed Booster" touted as part of the Drupal Platform 'BOA': https://groups.drupal.org/node/173219 and https://omega8.cc/features . 

The purpose of the header seems to be nothing more than a debug header to check which key has been used to retrieve the cached version in Speed Booster.

You probably want to contact your hosting company to see if they can disable that header.