https://www.reddit.com/r/Steam/comments/5skfg4/warning_regarding_a_steam_profile_related_exploit/

There's currently an exploit that's being used by just clicking on Steam profile links and/or viewing your activity feed that can cause bad stuff like phishing, malware, etc.

Because of this, do not click on any Steam links whatsoever (including on the web browser, desktop app, mobile site, and the mobile app).