During last months the project manager (PM) from a client requested many times to remove some security features we put on their web portal to “ease our day-by-day operativity” (their own words).
Initially these requests were calm and we managed to stop them. After a while PM became more pressing, so I (as the team leader of the project) wrote a detailed email with clear evidence of the dangers that could be incurred by meeting their demands (I copied my boss, my team, our IT security division, our test/QA division and their boss). After a few days PM replied to me only (all other recipients removed) in a very unprofessional way (all capital letter sentences, direct and personal insults, threats of lawsuits for incompetence, etc) ordering me to apply their requests or “to be prepared to face very serious consequences” (again their own words, capital letters removed by me). I immediately discussed the topic with my boss and she suggested to do what PM had requested and she would have sent an email (with all the previous recipients copied) saying we did all the requests but stressing again our concerns. So I removed the security features and she wrote the email.
From that day to yesterday, total silence. Yesterday morning PM wrote me that their security team found out someone entered illegally in the portal and some private data from their customers was found online. PM also said that this was “all my fault” because they were unaware of the possible consequences of “your choice to disable our portal security features”. Looking at how PM described what had happened, I noticed that this was (literally, step by step) one of the scenarios I highlighted as a potential security threat. I went to my boss again, and she decided that we had enough of PM. So for next week she will organize a call to discuss the situation with me, she, our division general manager (2 levels above my boss, so 3 above me), a senior coworker from our security division, PM and their boss.
Although I think I did nothing wrong and I can count on my boss, I'm also afraid there may be consequences for me. How can I be fully prepared for this important call and cover my back? How should I behave during it?