I had an app which was successfully opening Instagram with the image and caption already complete, but since updating to Instagram app 7.3 last night the caption is no longer filled.
Is there an update to the iphone hook I need to take in to account or is there a change to Interaction controller coming which they have adapted for and I haven't
Yeah, they removed pre-filled captions from mobile sharing.
But they say it does not break things, the caption is just ignored:
This is a non-breaking change: existing mobile apps that utilize pre-filled captions will continue to be able to use this flow to share media through the Instagram apps, but now Instagram will ignore the caption text.
http://developers.instagram.com/post/125972775561/removing-pre-filled-captions-from-mobile-sharing