diff --git a/src/query/validator.rs b/src/query/validator.rs
index e9e6e50..89a3f4f 100644
--- a/src/query/validator.rs
+++ b/src/query/validator.rs
@@ -2,8 +2,8 @@ use std::collections::HashSet;
 
 use anyhow::{anyhow, Result};
 use sqlparser::ast::{
-    Expr, Function, FunctionArg, FunctionArgExpr, FunctionArguments, ObjectName, Query, SetExpr,
-    Statement, TableFactor, TableWithJoins,
+    Expr, Function, FunctionArg, FunctionArgExpr, FunctionArgumentClause, FunctionArguments,
+    GroupByWithModifier, ObjectName, Query, SetExpr, Statement, TableFactor, TableWithJoins,
 };
 use sqlparser::dialect::GenericDialect;
 use sqlparser::parser::Parser;
@@ -207,10 +207,16 @@ fn validate_set_expr(
                 validate_expr(selection, cte_names, depth)?;
             }
 
-            // Validate GROUP BY expressions
-            if let sqlparser::ast::GroupByExpr::Expressions(exprs, _) = &select.group_by {
-                for expr in exprs {
-                    validate_expr(expr, cte_names, depth)?;
+            // Validate GROUP BY expressions and modifiers (GROUPING SETS, ROLLUP, CUBE)
+            match &select.group_by {
+                sqlparser::ast::GroupByExpr::Expressions(exprs, modifiers) => {
+                    for expr in exprs {
+                        validate_expr(expr, cte_names, depth)?;
+                    }
+                    validate_group_by_modifiers(modifiers, cte_names, depth)?;
+                }
+                sqlparser::ast::GroupByExpr::All(modifiers) => {
+                    validate_group_by_modifiers(modifiers, cte_names, depth)?;
                 }
             }
 
@@ -610,6 +616,66 @@ fn is_allowed_function(name: &str) -> bool {
     ALLOWED_FUNCTIONS.contains(&bare_name)
 }
 
+/// Recursively validate expressions inside GROUP BY modifiers (GROUPING SETS, etc.)
+fn validate_group_by_modifiers(
+    modifiers: &[GroupByWithModifier],
+    cte_names: &HashSet<String>,
+    depth: usize,
+) -> Result<()> {
+    for modifier in modifiers {
+        if let GroupByWithModifier::GroupingSets(expr) = modifier {
+            validate_expr(expr, cte_names, depth)?;
+        }
+    }
+    Ok(())
+}
+
+/// Maximum allowed length argument for string amplification functions (lpad, rpad, repeat).
+const MAX_STRING_PAD_LENGTH: i64 = 100_000;
+
+/// Functions whose first numeric argument (length/count) must be capped to prevent
+/// memory exhaustion via string amplification.
+const STRING_AMPLIFICATION_FUNCTIONS: &[&str] = &["lpad", "rpad", "repeat"];
+
+/// Validate that string amplification functions (lpad, rpad, repeat) don't have
+/// excessively large length arguments that could exhaust memory.
+fn validate_string_amplification(func_name: &str, func: &Function) -> Result<()> {
+    let bare_name = func_name.rsplit('.').next().unwrap_or(func_name);
+    if !STRING_AMPLIFICATION_FUNCTIONS.contains(&bare_name) {
+        return Ok(());
+    }
+
+    if let FunctionArguments::List(arg_list) = &func.args {
+        // The length/count argument is the 2nd arg for lpad/rpad, 2nd for repeat
+        let length_arg_idx = match bare_name {
+            "lpad" | "rpad" => 1, // lpad(string, length, [fill])
+            "repeat" => 1,       // repeat(string, count)
+            _ => return Ok(()),
+        };
+
+        if let Some(arg) = arg_list.args.get(length_arg_idx) {
+            if let FunctionArg::Unnamed(FunctionArgExpr::Expr(Expr::Value(v)))
+            | FunctionArg::Named {
+                arg: FunctionArgExpr::Expr(Expr::Value(v)),
+                ..
+            } = arg
+            {
+                if let sqlparser::ast::Value::Number(n, _) = &v.value {
+                    if let Ok(num) = n.parse::<i64>() {
+                        if num > MAX_STRING_PAD_LENGTH {
+                            return Err(anyhow!(
+                                "Function '{bare_name}' length argument {num} exceeds maximum ({MAX_STRING_PAD_LENGTH})"
+                            ));
+                        }
+                    }
+                }
+            }
+        }
+    }
+
+    Ok(())
+}
+
 fn validate_function(func: &Function, cte_names: &HashSet<String>, depth: usize) -> Result<()> {
     let func_name = func.name.to_string().to_lowercase();
 
@@ -617,6 +683,9 @@ fn validate_function(func: &Function, cte_names: &HashSet<String>, depth: usize)
         return Err(anyhow!("Function '{}' is not allowed", func_name));
     }
 
+    // Check string amplification functions for excessive length arguments
+    validate_string_amplification(&func_name, func)?;
+
     if let FunctionArguments::List(arg_list) = &func.args {
         for arg in &arg_list.args {
             if let FunctionArg::Unnamed(FunctionArgExpr::Expr(expr))
@@ -628,6 +697,15 @@ fn validate_function(func: &Function, cte_names: &HashSet<String>, depth: usize)
                 validate_expr(expr, cte_names, depth)?;
             }
         }
+
+        // Validate expressions inside function argument clauses (e.g. ORDER BY within aggregates)
+        for clause in &arg_list.clauses {
+            if let FunctionArgumentClause::OrderBy(order_exprs) = clause {
+                for order_expr in order_exprs {
+                    validate_expr(&order_expr.expr, cte_names, depth)?;
+                }
+            }
+        }
     }
 
     // Validate FILTER (WHERE ...) clause
@@ -1014,4 +1092,85 @@ mod tests {
             validate_query("SELECT * FROM blocks FETCH FIRST 10 ROWS ONLY").is_err()
         );
     }
+
+    // === Audit finding: GROUPING SETS bypasses function allowlist ===
+
+    #[test]
+    fn test_rejects_set_config_in_grouping_sets() {
+        assert!(validate_query(
+            "SELECT 1 FROM blocks GROUP BY ALL GROUPING SETS ((set_config('a','b',true)))"
+        )
+        .is_err());
+    }
+
+    #[test]
+    fn test_rejects_dangerous_function_in_grouping_sets_with_expressions() {
+        assert!(validate_query(
+            "SELECT num FROM blocks GROUP BY num GROUPING SETS ((pg_sleep(1)))"
+        )
+        .is_err());
+    }
+
+    #[test]
+    fn test_allows_normal_group_by() {
+        assert!(validate_query("SELECT num, COUNT(*) FROM blocks GROUP BY num").is_ok());
+        assert!(validate_query(
+            "SELECT num, COUNT(*) FROM blocks GROUP BY ALL"
+        )
+        .is_ok());
+    }
+
+    // === Audit finding: Aggregate ORDER BY bypasses function allowlist ===
+
+    #[test]
+    fn test_rejects_set_config_in_aggregate_order_by() {
+        assert!(validate_query(
+            "SELECT string_agg(hash, ',' ORDER BY set_config('a','b',true)) FROM blocks"
+        )
+        .is_err());
+    }
+
+    #[test]
+    fn test_rejects_pg_sleep_in_aggregate_order_by() {
+        assert!(validate_query(
+            "SELECT array_agg(num ORDER BY pg_sleep(1)) FROM blocks"
+        )
+        .is_err());
+    }
+
+    #[test]
+    fn test_allows_normal_aggregate_with_order_by() {
+        assert!(validate_query(
+            "SELECT string_agg(hash, ',' ORDER BY num) FROM blocks"
+        )
+        .is_ok());
+        assert!(validate_query(
+            "SELECT array_agg(num ORDER BY num DESC) FROM blocks"
+        )
+        .is_ok());
+    }
+
+    // === Audit finding: lpad/rpad/repeat memory exhaustion ===
+
+    #[test]
+    fn test_rejects_lpad_huge_length() {
+        assert!(validate_query("SELECT lpad('x', 999999999) FROM blocks").is_err());
+    }
+
+    #[test]
+    fn test_rejects_rpad_huge_length() {
+        assert!(validate_query("SELECT rpad('x', 999999999) FROM blocks").is_err());
+    }
+
+    #[test]
+    fn test_rejects_repeat_huge_count() {
+        assert!(validate_query("SELECT repeat('x', 999999999) FROM blocks").is_err());
+    }
+
+    #[test]
+    fn test_allows_lpad_rpad_small_length() {
+        assert!(validate_query("SELECT lpad(hash, 66, '0') FROM blocks").is_ok());
+        assert!(validate_query("SELECT rpad(hash, 66, '0') FROM blocks").is_ok());
+        assert!(validate_query("SELECT repeat('0', 10) FROM blocks").is_ok());
+    }
 }