Several million Snapchat usernames and phone numbers were apparently leaked online late Dec., 31, 2013. Several outlets reported that 4.6 million usernames and phone numbers were posted as a downloadable database by hackers, but the site where the database was posted appeared to be down on Wednesday morning, USA Today reports.

Days prior, Snapchat – a popular messaging app that lets users send each other photos that quickly disappear – warned users of this potential scenario in a blog post, saying a security group had alerted it about a potential vulnerability “by which one could compile a database of Snapchat usernames and phone numbers.” The company said that it had implemented safeguards making an exploit “more difficult to do.”

The data gleaned from Snapchat could be very valuable, as phone numbers and corresponding names and other records could be used at call centers, or for social-engineering attacks and identity fraud.

According to Roger Thompson, chief emerging threat researcher at ICSA Labs, a vendor-neutral testing and certification firm, "Security and functionality tend to exist in an inverse relationship – the more functional you make a system, the less secure it tends to be. Web-based systems like Snapchat are built for functionality, so we should not be surprised that hackers found a vulnerability in a new, highly-functional system. The hole will be patched, and hackers will look for new ones. It's almost a cost of doing business. The moral of the story is that we have to be thoughtful about what information we put online, because it might just leak, and we should only use one password per website. Password re-use is your enemy.”

Meanwhile, the official blog and social networking accounts for Microsoft’s Web calling service Skype appear to have been breached – a post published Wednesday on the official Skype blog featured the headline: “Hacked by Syrian Electronic Army.. Stop Spying!” A pair of tweets attributed to the SEA were then posted on Skype’s official Twitter account, and Skype’s Facebook page hosted a message accusing Microsoft of monitoring email accounts (Hotmail, Outlook) and selling the information to government sources.

Skype has reported that no user information was compromised.