add_metadata() Fails to Store Serialized Values as BINARY

[miqrogroove]

Symptoms:

WordPress stores corrupt values in post_metadata if there are any non-UTF-8 bytes in the meta_value.

Steps to reproduce:

Call add_metadata() with non-UTF-8 values such as a latin-1 copyright char.

Even though the serialized string goes through prepare() before the query, MySQL is required to truncate the invalid value being assigned to the meta_value field. The result is that the stored value can never be un-serialized.

This behavior can also be replicated by trying to inject CHAR(169) into any UTF-8 table query.

After giving this some thought, I've come to the conclusions:

1. Post metas are not binary-safe.

2. There is no way to make them binary-safe without converting all existing values to a proper binary column.

similar bugs referenced here: #9549

Shifting to Future release pending patch, Too close to release to be changing anything related to the Schema anyway.