The authenticity of any text used to haunt the ancients. Hinduism has faced this problem in the past. In the ancient world no text was safe from modification because of the absence of the printing technology. So Hindu scriptures have given us guidelines to follow.
Everything written in Hindu scripture is not valid. A scriptural statement can be invalid if it does not satisfy reason.
Primacy of reason
Even the words heard from an ignorant person, if in themselves they be
fraught with sense, come to be regarded as pious and wise. In days of
old, Usanas said unto the Daityas this truth, which should remove all
doubts, that scriptures are no scriptures if they cannot stand the
test of reason.
Mahabharata Shanti Parva Section CXLII
Acharya Shankara says:
The appeal to the infallibility of the Vedic injunction is
misconceived. The infallibility in question refers only to the unseen
forces or apurva, and is admissible only in regards to matters not
confined to the sphere of direct perceptions, etc ... Even a hundred
statements of sruti to the effect that fire is cold and non-luminous
won't prove valid. If it does make such a statement, its import will
have to be interpreted differently. Otherwise, validity won't attach
to it. Nothing in conflict with the means of valid cognition or with
its own statements may be imputed to sruti.
REF: Srimad Bhagavad Gita Bhasya 18.66 of Sri Sankaracarya translation by Dr. A. G. Krishna Warrier, p. 629.
Rejection of discriminatory verses
Any discriminatory verse in Hindu scripture is also automatically invalid according to Hindu scripture and should not be followed. This is necessary because Hinduism is not an organized dharma and does not have any central body to oversee the content of Hindu spiritual texts.
If a holy act is against the interest of other members of the society,
it should not be practiced. It is Dharma which is the source of Artha
and even of Kama.
Kurma Purana I.2.54
The implication of the Kurma Purana verse is that the hereditary caste system practiced by Hindus is an invalid system on the grounds of discrimination. So if you think that the Chandogya Upanishad V.10.7 is discriminatory then you can regard that shloka as invalid regardless of its authenticity.
However, I don't think the Chandogya shloka is discriminatory. Read my post on this issue:
Is it justified to Outcaste Chandalas?