Preface: Excel spreadsheets are used all the time in high-risk financial data analysis, and sometimes this is a silent way to dig out the data.

BlackRock data leakage synopsis:

Bloomberg found three spreadsheets contains BlackRock’s iShares ETF business confidential information included thousands of financial advisors were given ratings based on how much business they bring BlackRock. For more details, please refer below url:
https://www.bloomberg.com/news/articles/2019-01-19/blackrock-exposes-data-on-thousands-of-advisers-on-ishares-site

Is it a careless mistake?
It is hard to tell. From technical point of view, Blackrock is easy to figure out the problem though their spreadsheet management system.

Prediction:
If it didn’t find related suspicious activity in the spreadsheet management system and security incident event management? What is the next step? Do the dark web research may find out some hints. If the final confirmation is a user negligence. In a nutshell, user negligence shown the design weakness of awareness training program.