The Dutch police recently arrested a developer for crimes he committed by writing a website backdoor into e-commerce sites he created and using credentials retained after the engagement concluded. This backdoor provided the malicious insider with sufficient access to perpetrate a number of crimes by leveraging 20,000 users credentials. The developer was counting on the majority of users to exhibit poor online hygiene. He was able to breach social media and other external accounts because many customers reused login credentials across multiple services. Users must protect those social network and email credentials like the golden keys they are.”]
Source: https://securityintelligence.com/did-your-developer-leave-a-website-backdoor/