AiS 22: Website Attacks

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Cross site scripting and SQL injection attacks both take advantage of vulnerabilities in websites. In the case of a cross site scripting vulnerability, data can be rendered to the browser, causing it to run unintended code. In the case of a SQL injection attack, data is executed by the database as SQL code. In both cases, input that a malicious user provides is interpreted in a way that the designer did not intend.

Both of these vulnerabilities are software defects. In both cases, data in a natural language is rendered as if it were a programming language. Web developers and designers need to take extra precautions to prevent this from happening. But what are the right precautions?

One solution is to validate all inputs to ensure that no script or SQL code is included. Unfortunately, this approach is nearly impossible to implement correctly. Any inconsistencies between the way the validator parses the input and the way the browser or database interprets it can leave a hole for a hacker to slip through. Furthermore, it may be perfectly valid for the data to contain HTML or SQL code. What if you are running a blog about software? Shouldn't you be able to post code to the blog?

A better solution is to escape the data. If you are converting a natural language string into SQL, you have to be sure to escape the quotes. In HTML, you must escape the angle brackets. Several tools are already at your disposal to perform the escaping function. Please take full advantage of them.

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