It is currently unclear whether added/ removed attachments in bugzilla are listed as changes when one looks for all changes with certain criteria.
The attachment object is described here:
https://wiki.mozilla.org/Bugzilla:REST_API:Objects#Attachment
Note: there may be unexpected behaviour with attachments; in the introduction notes, there is the following
"A general API principle is that if you don't submit a field or object to a change function, it's unchanged. This means you can send simple changes without having to send the entire bug. However, due to limitations of Bugzilla, this does not work with attachments - you need to send the whole object."
https://wiki.mozilla.org/Bugzilla:REST_API:Objects
It might be worth having a short spike on attachments once some of the other stories have been done.