GHSA-gcjh-h69q-9w9g

The function `ext.NativeTypes(ParseStructTag("json"))` does not honour the `encoding/json` skip directive `json:"-"`. Fields tagged `json:"-"` are registered in the CEL type system under the literal name `"-"` and are readable from any user-submitted CEL expression via `dyn(obj)["-"]`. Additionally, `newNativeTypes` silently registers every nested struct reachable from the type passed to `NativeTypes`, including types from third-party dependencies the developer never examined. ## Root cause In `fieldNameByTag`, the helper used by `ParseStructTag("json")` to translate Go struct tags into CEL field names. See at `ext/native.go:146`: ```go func fieldNameByTag(structTagToParse string) func(field reflect.StructField) string { return func(field reflect.StructField) string { tag, found := field.Tag.Lookup(structTagToParse) if found { splits := strings.Split(tag, ",") if len(splits) > 0 { // We make the assumption that the leftmost entry in the tag is the name. // This seems to be true for most tags that have the concept of a name/key, such as: // https://pkg.go.dev/encoding/xml#Marshal // https://pkg.go.dev/encoding/json#Marshal // https://pkg.go.dev/go.mongodb.org/mongo-driver/bson#hdr-Structs // https://pkg.go.dev/go.yaml.in/yaml/v3#Marshal name := splits[0] return name } } return field.Name } } ``` For a field tagged `json:"-"`, this code splits the tag into `[]string{"-"}` and returns `"-"` as the CEL field name. It never checks whether `"-"` is the JSON skip sentinel. This contradicts the `encoding/json` rule that the source comment explicitly points readers to: ```text As a special case, if the field tag is "-", the field is always omitted. Note that a field with name "-" can still be generated using the tag "-,". ``` The public option also documents JSON-