利用用戶輸入構建動態的 XPath 查詢使攻擊者可借機修改語句的含義。
XPath injection 會在以下情況中出現：
1. 數據從一個不可信賴的數據源進入程序。
2. 數據用于動態構造一個 XPath 查詢。
例 1：下列代碼可動態地構建并執行一個 XPath 查詢，為指定的帳戶 ID 檢索電子郵件地址。由于該帳戶 ID 是從 HTTP 請求中讀取的，因此不可信賴。
...
string acctID = Request["acctID"];
string query = null;
if(acctID != null) {
StringBuffer sb = new StringBuffer("/accounts/account[acctID='");
sb.append(acctID);
sb.append("']/email/text()");
query = sb.toString();
}
XPathDocument docNav = new XPathDocument(myXml);
XPathNavigator nav = docNav.CreateNavigator();
nav.Evaluate(query);
...
/accounts/account[acctID='1']/email/text()acctID 不含單引號字符時，查詢才會正確執行。如果攻擊者為 acctID 輸入字符串 1' or '1' = '1，則該查詢會變成：/accounts/account[acctID='1' or '1' = '1']/email/text()1' or '1' = '1 會使 where 從句永遠評估為 true，因此，該查詢在邏輯上等同于更簡單的查詢：//email/text()[1] Standards Mapping - OWASP Top 10 2010 - (OWASP 2010) A1 Injection
[2] Standards Mapping - OWASP Top 10 2007 - (OWASP 2007) A2 Injection Flaws
[3] Standards Mapping - OWASP Top 10 2004 - (OWASP 2004) A6 Injection Flaws
[4] Standards Mapping - Security Technical Implementation Guide Version 3 - (STIG 3) APP3510 CAT I
[5] Standards Mapping - Security Technical Implementation Guide Version 3.4 - (STIG 3.4) APP3510 CAT I
[6] Standards Mapping - Common Weakness Enumeration - (CWE) CWE ID 643
[7] Standards Mapping - Payment Card Industry Data Security Standard Version 1.2 - (PCI 1.2) Requirement 6.3.1.1, Requirement 6.5.2
[8] Standards Mapping - Payment Card Industry Data Security Standard Version 2.0 - (PCI 2.0) Requirement 6.5.1
[9] Standards Mapping - Payment Card Industry Data Security Standard Version 1.1 - (PCI 1.1) Requirement 6.5.6
[10] Standards Mapping - FIPS200 - (FISMA) SI
[11] Standards Mapping - Web Application Security Consortium 24 + 2 - (WASC 24 + 2) XPath Injection