why hackers can decrypt my encrypted Connection String in web.config(C#)

My application is on the shared Hosting.I've encrypted my Connect开发者_如何学JAVAion String programmatically to make it secure. However, the hacker still is able to decrypt the encrpted Connection String adding scripts into the DB. Just wondering if there is a way to solve this problem? Many thanks !!!

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.NET vulnerability discovered last September.

Make sure your .NET is up to date!

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If the hacker gains control over your server, he can do anything your code can do. Can your code decrypt the Connection String? (apparently yes) Then he can do it, too.