We advise you to change your Instagram password because of Instagram third-party app “InstaAgent”, which allows you to see who viewed your profile.
David Layer-Reiss - a German iOS developer - posted a series of tweets that included evidence InstaAgent was "hacking" people's details and posting pictures on their account without even asking for their permission.
InstaAgent is quite popular in some markets — in Germany for example; it was among the top 30 most popular apps. It's hard to figure out the exact number of compromised accounts, but Layer-Reiss claims more than 500,000 users installed the app.
Furthermore, Apple and Google play pulled off the App from their stores after proving the hacking.