What is Buddhism's secret text?

Answer 1

*looks around* Secret book? we have a secret book? If so no one brought it to my attention...

Seriously, as far as I know The Buddha made clear his teachings in full to all that asked. He presented his teachings in a number of formats based upon the people he was talking with. So more advanced followers he would explain things in a more complex manner and for newer followers he used simpler language and examples, but in all cases the teachings were that same.

Answer 2

Buddhism does not have a single "secret text." The teachings of Buddhism are primarily found in the Tripitaka, also known as the Pali Canon, which is a collection of scriptures containing the Buddha's discourses. There are also various Mahayana sutras and Tibetan Buddhist texts that are considered significant in different Buddhist traditions. However, these texts are not regarded as secret, but rather available for study and practice by anyone interested in Buddhism.