imgur.com has recently added a feature where gifs can have audio. When a user pastes a link to a gif, and they have audio enabled on that gif in imgur, the HipChat client will loop that audio. The audio cannot be muted in HipChat unless the gif is hidden or the user leaves the channel the gif is in. 

 

steps:

go to https://imgur.com/gallery/AuRx1KN

enable sound on the gif

close the browser

paste the same gif, with sound enabled, into a HipChat conversation

 

actual: the gif audio starts playing though the HipChat client. it cannot be muted.

expected: might need a setting for gifs with audio?

Haven't tested this for the mobile or webclients, but it's def an issue in both windows and mac.