Earlier, security researchers scanned the system for fear of risk from the recent Shellshock vulnerability and discovered the Yahoo! risk of being attacked. Then they contacted Yahoo! to warn. Yahoo! immediately checked and found that my server was compromised through a security hole, but not Shellshock.
"After a full investigation, we concluded that the Yahoo! server is in fact not directly affected by Shellshock, but another vulnerability. We did not find any user information. affected by this problem, "Yahoo! said to BBC News.
In another statement, Yahoo! Alex Stamos revealed that the company has also added a number of tools to "capture security issues" in the future.