Your Rocket.Chat version: 0.26

Search seems to be working only on the text of the post and not on anything inside an attachment.
This is quite a limitation when using integrations (e.g. - posting form gitlab on an alerting system. You want to use attachment to format the post in a readable way, using fields to better structure the data. But search does not work on the attachment so you can't search by the data in these fields).