fix(fuzz): use actual parameter for frequency dedupe (projectdiscovery#7037)

Fix numeric path fuzz dedupe by using actualParameter for frequency
checks and add regression tests for numeric index and actual value
behavior.

Author: Godzilla675

pkg/fuzz/parts.go

@@ -162,7 +162,7 @@ func (rule *Rule) execWithInput(input *ExecuteRuleInput, httpReq *retryablehttp.
 	// If the parameter is frequent, skip it if the option is enabled
 	if rule.options.FuzzParamsFrequency != nil {
 		if rule.options.FuzzParamsFrequency.IsParameterFrequent(
-			parameter,
+			actualParameter,
 			httpReq.String(),
 			rule.options.TemplateID,
 		) {

pkg/fuzz/parts_frequency_test.go

@@ -0,0 +1,77 @@
+package fuzz
+
+import (
+	"net/http"
+	"testing"
+
+	"github.com/projectdiscovery/nuclei/v3/pkg/fuzz/frequency"
+	"github.com/projectdiscovery/nuclei/v3/pkg/protocols"
+	retryablehttp "github.com/projectdiscovery/retryablehttp-go"
+	"github.com/stretchr/testify/require"
+)
+
+// TestExecWithInputDoesNotUseNumericParameterIndexForFrequency verifies frequency
+// checks do not key on numeric path segment indexes.
+func TestExecWithInputDoesNotUseNumericParameterIndexForFrequency(t *testing.T) {
+	tracker := frequency.New(64, 1)
+	defer tracker.Close()
+
+	const target = "https://example.com/users/55"
+	const templateID = "tmpl-frequency-check"
+
+	req, err := retryablehttp.NewRequest(http.MethodGet, target, nil)
+	require.NoError(t, err)
+
+	tracker.MarkParameter("2", req.String(), templateID)
+
+	called := false
+	rule := &Rule{
+		options: &protocols.ExecutorOptions{
+			TemplateID:          templateID,
+			FuzzParamsFrequency: tracker,
+		},
+	}
+	input := &ExecuteRuleInput{
+		Callback: func(GeneratedRequest) bool {
+			called = true
+			return true
+		},
+	}
+
+	err = rule.execWithInput(input, req, nil, nil, "2", "55", "", "", "", "")
+	require.NoError(t, err)
+	require.True(t, called, "numeric path index should not be used as frequency key")
+}
+
+// TestExecWithInputSkipsWhenActualParameterIsFrequent verifies requests are
+// skipped when the normalized parameter value is marked frequent.
+func TestExecWithInputSkipsWhenActualParameterIsFrequent(t *testing.T) {
+	tracker := frequency.New(64, 1)
+	defer tracker.Close()
+
+	const target = "https://example.com/users/55"
+	const templateID = "tmpl-frequency-check"
+
+	req, err := retryablehttp.NewRequest(http.MethodGet, target, nil)
+	require.NoError(t, err)
+
+	tracker.MarkParameter("55", req.String(), templateID)
+
+	called := false
+	rule := &Rule{
+		options: &protocols.ExecutorOptions{
+			TemplateID:          templateID,
+			FuzzParamsFrequency: tracker,
+		},
+	}
+	input := &ExecuteRuleInput{
+		Callback: func(GeneratedRequest) bool {
+			called = true
+			return true
+		},
+	}
+
+	err = rule.execWithInput(input, req, nil, nil, "2", "55", "", "", "", "")
+	require.NoError(t, err)
+	require.False(t, called, "frequent actual parameter should be skipped")
+}