fix index out of range error (#4998)

pkg/fuzz/dataformat/form.go

@@ -94,20 +94,35 @@ func (f *Form) Encode(data KV) (string, error) {
 					}
 				}
 			}
+			if maxIndex >= 0 { // Ensure the slice is only created if maxIndex is valid
 				data := make([]string, maxIndex+1) // Ensure the slice is large enough
 				for key, value := range v {
 					matches := reNormalized.FindStringSubmatch(key)
 					if len(matches) == 2 {
-					dataIdx, _ := strconv.Atoi(matches[1]) // Error already checked above
+						dataIdx, err := strconv.Atoi(matches[1]) // Error already checked above
+						if err != nil {
+							gologger.Verbose().Msgf("error converting data index to integer: %v", err)
+							continue
+						}
+						// Validate dataIdx to avoid index out of range errors
+						if dataIdx > 0 && dataIdx <= len(data) {
 							data[dataIdx-1] = value // Use dataIdx-1 since slice is 0-indexed
+						} else {
+							gologger.Verbose().Msgf("data index out of range: %d", dataIdx)
 						}
 					}
+				}
+				if len(params.Get(k)) > 0 {
 					data[maxIndex] = fmt.Sprint(params.Get(k)) // Use maxIndex which is the last index
+				}
 				// remove existing
 				params.Del(k)
+				if len(data) > 0 {
 					params.Add(k, data...)
 				}
 			}
+		}
+	}
 
 	encoded := params.Encode()
 	return encoded, nil