Solve : URL encoding/decoding question.?

1.	Solve : URL encoding/decoding question.?
Answer» This is an example from a BOOK I've read, but I don't understand how it works. A WEB admin may attempt to block SQL injections by blocking input CONTAINING the apostrophe character. However, an input containing double encoding may be able to defeat the filter. eg : %2527 Why is this so ? The book stated that %2527 will become %27 after decoding it. What's the process behind it ? GUIDANCE is appreciated

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