# SQL injection overview ## What is it? SQL injection is where an attacker is able to manipulate database queries made by an application. **A simple example** * A vulnerable web application has the endpoint `/search?product={productName}` * When a request is made, the application uses SQL to search for the product `SELECT * FROM products WHERE name=$productName` * If an attacker inserts a payload into `{productName}` such as `anything' UNION SELECT password FROM users WHERE username = 'admin` that modifies the query, sensitive data could be leaked. * The vulnerable application sends this query to the database and the database returns the admin's password. It's important to note that a payload or attack may change depending on the application, the query, and the database. SQL injection can often lead to: * Sensitive data exposure * Data manipulation * Remote code execution * Denial of service **Other learning resources:** * PostSwigger: * Swisskeyrepo: **Writeups:** * *Have a good writeup & want to share it here? Drop me a message on LinkedIn.* ## Checklist * [ ] What is the technology stack you're attacking? * [ ] What application/framework is being used * [ ] What backend DB is being used * [ ] Is there an ORM? * [ ] Verify injection points * [ ] URL parameters * [ ] Form fields * [ ] HTTP headers (e.g. cookies, etc) * [ ] Out-of-band (e.g. data retrieved from a third party) * [ ] Test ' and " * [ ] Can you trigger an error? * [ ] Can you trigger a different response? * [ ] Test with SQLmap * [ ] Test for login bypass `' and 1=1-- -` etc * [ ] Test for blind SQLi * [ ] Test for errors * [ ] Test for conditional responses * [ ] Test for conditional errors * [ ] Test for time delays * [ ] Test for out-of-band interactions * [ ] Test for NoSQL injection * [ ] Is there a blocklist? * [ ] Can you bypass the blocklist? * [ ] Encoding * [ ] Double encoding * [ ] Alternative characters * [ ] Alternative payloads * [ ] Test for second-order SQLi ## Exploitation ```sql # Basic login bypass ' AND 1=1# ``` ```sql # UNION SELECT ' UNION SELECT null,null FROM users-- - ``` ```sql # Blind ' AND SUBSTR((SELECT version()),1,1)='7'# CAST((SELECT example_column FROM example_table) AS int) ``` --- # Agent Instructions: Querying This Documentation If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question. Perform an HTTP GET request on the current page URL with the `ask` query parameter: ``` GET https://appsecexplained.gitbook.io/appsecexplained/common-vulns/sql-injection-overview.md?ask= ``` The question should be specific, self-contained, and written in natural language. The response will contain a direct answer to the question and relevant excerpts and sources from the documentation. Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.