general PSA: there is/was an exploit in steam that can cause hackers to hijack your steam account. several steam accounts have already been claimed using this (such as dota 2 player arteezy's, according to both his twitter and his manager claiming a fix is being worked on or is out already).
reminder that steam guard is easy to turn on and use, and there's no reason to not have it on at this point. the steam app on android/ios supports full two-factor authentication now and it's recommended to download it from respective app stores and activate mobile guard.
EDIT: the bug is fixed now, but please take this post as a steam guard reminder anyway
EDIT2: added more sources