Microsoft has again disabled the ms-appinstaller protocol handler by default due to its abuse by cybercriminals to spread malware. Financially motivated hacking groups and cybercriminals have used it as an entry point for ransomware activity since mid-November 2023. The changes are applicable to App Installer version 1.21.3421.0 or higher. The attacks often involve distributing malicious MSIX app packages via Microsoft Teams or through misleading adverts for legitimate software on search engines.

Jingle Thief Attackers Exploiting Festive Season with Weaponized Gift Card Attacks
As the festive season approaches, organizations are witnessing a disturbing increase in targeted attacks on digital gift card systems. The Jingle Thief campaign, orchestrated by
