From the documentation of glDrawArrays:
Vertex attributes that are modified by glDrawArrays have an unspecified value after glDrawArrays returns. Attributes that aren't modified remain well defined.
I understand that glDrawArrays uses buffer data and some information about how to interpret the data as vertices in order to draw graphics. What I don't understand is how this can result in modifiying vertex attributes.
I am seeing some strange values in my vertex buffer data, after I map it with glMapBufferRange, and I'm trying to track down where the unexpected values could be originating from.