Historically, Skype has faced legitimate security issues that hackers exploited. These were fixed by Microsoft and did not involve "activation codes" for the public:
: Some malicious tools may even install ransomware, locking you out of your device until a fee is paid. Known Skype Vulnerabilities Skype+hacker+activation+code
The phrase typically refers to a common online scam or a deceptive bait used by malicious actors to target unsuspecting users. These "activation codes" are often marketed as tools to bypass Skype’s security, unlock premium features for free, or even gain unauthorized access to other people's accounts. unlock premium features for free