The square boxes as you call them are most likely caused by special characters being encoded in the JSON string.
Your not giving many clues as how you are getting the data into the string, what the string looks like, or how you are trying to use the string in your app, making it difficult to give any specific answer.
Pass the string through a function to cleanse is an option depending on how you are trying to do things.
If you are using the JSON javascript library, there in the stringify and parse methods there is an optional callback replacer and reviver where you can pass the string through to special functions to do any custom operations.
See;
http://www.json.org/js.html[
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