GHSA-97r2-qh9m-474h

### Summary `fromJSON` and `fromCrossJSON` used two node fields without checking them. - An array node's element list was not checked to be an array. A small payload could set the length the decoder looped over. This part is also tracked in GHSA-wp97-x4hv-qvhp. - A sequence node's done index was not checked. A crafted value produced an iterator that never finished. ### Impact A service that passes untrusted input to `fromJSON` or `fromCrossJSON` can be made unavailable by an unauthenticated request. - The array case blocks the thread while the decoder runs. - The sequence case makes any code that reads the resulting iterator to the end run forever. ### Patches Fixed in `[email protected]`. - Element lists must be arrays. - A sequence node's throw and done indices must be integers from -1 up to the last element index. Invalid input throws `SerovalMalformedNodeError`. ### Workarounds None. Upgrade to 1.6.8.