<p>NSW Police have described it as ''the number one social media problem involving teenagers'' - but most parents would barely have heard of messaging app Kik before this week.</p><p>Kik's popularity among young people was highlighted by the disappearance of Sydney teenager Krystal Muhieddine, who left her house early on Tuesday morning in a car with a stranger before being found in country Victoria on Friday.</p><p>Krystal's parents did not allow their children to use social media in the house, but Mrs Muhieddine said she believed her 14-year-old daughter had been using Kik to communicate with the person with whom she left.</p><p>Kik is a free texting app used by more than 50 million people around the world that enables users to connect with strangers. Although rated for people aged 17 and older, experts say children aged 11-15 are its main users.</p><p><a href="http://www.smh.com.au/national/police-warning-on-social-media-messaging-app-kik-20131130-2yimo.html">Keep reading...</a></p><p>Read also:</p><p><a href="http://www.northqueenslandregister.com.au/news/metro/national/general/experts-warn-of-apps-hidden-dangers/2680258.aspx">Experts warn of app&#039;s hidden dangers</a> (North Queensland Register)</p><p><a href="http://www.stockandland.com.au/news/metro/national/general/krystal-muhieddine-found-safe-was-scared/2680256.aspx">Krystal Muhieddine found safe, was scared</a> (Stock &amp; Land)</p><p>Explore: <a href="http://news.google.com/news/more?ncl=dPOrEztnLANwhsM1Y6i_xZcrn_P0M&ned=us">7 additional articles.</a></p>