This update fixes an old NULL pointer dereference bug in png_set_text_2() discovered and patched by Patrick Keshishian. The potential “NULL dereference” bug has existed in libpng since version 0.71 of June 26, 1995. To be vulnerable, an application has to load a text chunk into the png structure, then delete all text, then add another text chunk to the same png structure, which seems to be an unlikely sequence, but it has happened.

The update also fixes some documentation typos and an instance of undefined behavior.