The devs (should) have known about these security risks for at least one year: Cheating and Security of Aoe DE II
A german hacker-team found security issues and reported them to the devs / Microsoft. I guess they told them also how they were able to exploit them (control enemy units, cancel opponent research, etc.).
Thus, it seems like malicious hackers were able to exploit the security issues faster than the devs were able to fix them. At least I hope that they are trying to fix them…