The author seems to assume that the reader shares his knowledge of who the pronoun refers to.
老师好,这里who是不是应该改为whom?
句的 who 可以换成 whom,但不是必须要改为 whom。
因为这里的介词 of 的宾语不是 who,而是 who the pronoun refers to(即接它作为宾语从句)。
句中的 who 是 refers to 的宾语。