Skype bug can't be fixed without a major rewrite

Gives an attacker system level privileges

Skype has a significant security flaw that Microsoft can't fix without a major code rewrite.

The flaw is in Skype's updater process can allow an attacker to gain system-level privileges to a vulnerable computer. If exploited, can escalate a local unprivileged user to the full "system" level rights -- granting them access to every corner of the operating system.