In this case, it clearly means that some of the quote has been omitted. The author might have found it distasteful or even purely unnecessary to add a word of low taste to the text.
It for sure doesn't not mean any extension, nor the dislike of the author with his own writing. Also, it makes no sense to say that the writer has changed the meaning of the quote.
So the correct answer must be: Some of the quote has been omitted
