通過利用用戶輸入構建動態 XQuery 表達式，攻擊者就能夠修改指令的含義。
XQuery 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 XQuery 表達式。
例 1：下列代碼能夠動態地構建和執行 XQuery 表達式，用來根據給定的用戶名和密碼組合檢索出用戶。由于用戶名和密碼通過 HTTP 請求讀取，因而是不可信的。
...
require_once 'zorba_api.php';
$memstor = InMemoryStore::getInstance();
$z = Zorba::getInstance($memstor);
try {
// get data manager
$dataman = $z->getXmlDataManager();
// load external XML document
$dataman->loadDocument('users.xml', file_get_contents('users.xml'));
// create and compile query
$express =
"for \$user in doc(users.xml)//user[username='" .$_GET["username"] ."'and pass='" .$_GET["password"] ."'] return \$user"
$query = $zorba->compileQuery($express);
// execute query
$result = $query->execute();
?>
...
for \$user in doc(users.xml)//user[username='test_user' and pass='pass123'] return \$userusername 或 password 不包含單引號字符時，才會正確執行這一查詢。如果攻擊者為 username 輸入字符串 admin' or 1=1 or ''='，則該查詢會變成：for \$user in doc(users.xml)//user[username='admin' or 1=1 or ''='' and password='x' or ''=''] return \$useradmin' or 1=1 or ''=' 會使 XQuery 表達式永遠評估為 true。因此，該查詢在邏輯上等同于更簡單的查詢：//user[username='admin'][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 652
[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