Hugo's default fenced-code-block renderer writes attribute values taken from the code-fence info string into the rendered HTML without escaping them. New in markup/internal/attributes/attributes.go c…

Summary

Hugo's default fenced-code-block renderer writes attribute values taken from the code-fence info string into the rendered HTML without escaping them. New in markup/internal/attributes/attributes.go converts every attribute value from a byte slice to a string as it is stored, deliberately dropping the escaping that used to happen there, and RenderAttributes in the same file escapes only values that are still byte slices, so its escaping branch is never reached and every value is written verbatim…