This article warns of a security flaw between the two social networks that can be compromised in certain circumstances.

http://www.cio.com/article/2459062/using-instagram-on-public-wifi-poses-risk-of-an-account-hijack-researcher-says.html

A configuration problem in Facebook’s popular Instagram application for Apple devices could allow a hacker to hijack a person’s account if they’re both on the same public Wi-Fi network. Stevie Graham, who describes himself as a “hacker at large” based in London, wrote on Twitter that Facebook won’t pay him a reward for reporting the flaw, which he said he found years ago.

Graham wrote he hopes to draw more attention to the issue by writing a tool that could quickly compromise many Instagram accounts. He cheekily calls the tool “Instasheep,” a play on Firesheep, a Firefox extension that can compromise online accounts in certain circumstances.

“I think this attack is extremely severe because it allows full session hijack and is easily automated,” according to Graham’s technical writeup. “I could go to the Apple Store tomorrow and reap thousands of accounts in one day, and then use them to post spam.”