With ever the constant updates to popular and important apps and websites, how do the developers ensure the update preserves the user and site's original database, considering the possibility that the updates might contain data-corruptive bugs or exploits for users?
This question is not addressing the frequent database leaks, since they only involve release of read only data and exploits only exist in the form of accessing user accounts and data, not altering the site's database at large itself.
Even if there is a backup for the database, undoing changes that affect millions or people negatively would create a ton of uproar, especially if the site is based on real time interactions, like stock broker apps, social media apps and instant messengers. However I have personally never heard of such incidents.
Do companies at such large scales have extreme QA in place, depend on user feedback and reporting, or just have been lucky they haven't been exploited yet? Or am I completely wrong and these incidents do occur?
Keep in mind that I am an amateur in this domain. I have worked with MySQL databases for educational purposes and personal projects but I found the state of databases very fragile, like the ability to nuke the entire database with just 2-3 words. This fact made me come up with this question.
This was entirely opposite of how I expected the state of product updates to be. I didn't know the devs expected for the worse to happen. Thank you for providing me with this insight.
Not exactly related to your question, but if you want to get an idea of how porous security is you might want to watch a few episodes of Security Now: https://twit.tv/shows/security-now