There are two changes here. First, in the 1837 edition the original past-participial form proved was replaced by the alternative proven. As explained under Alma 34:6, either form is possible in the Book of Mormon text.
The second change took place in the 1874 RLDS edition; there the third person singular hath was incorrectly replaced by the third person plural have. The 1874 typesetter apparently thought that the subject of the verb was “the people of the Nephites”, a plural noun phrase, when in fact the subject was the earlier singular pride. The 1908 RLDS edition restored the correct hath to the RLDS text.
Summary: Restore in Moroni 8:27 the original past-participial form proved; also maintain the singular hath, which is perfectly correct since the subject for hath is the singular noun pride.