[pdftex] \magnification & pdftex 1.30.4

[Bob Howlett]

Dear experts,

Our system administrator has just installed pdftex 1.30.4;
previously we had 1.11a. When I now run pdftex on a file
that just says

\magnification=\magstep1
Hello
\bye

the pdf file that I get has MediaBox that is 1.2 times
the size of the MediaBox that I got with the older
version of pdftex. It is as though the configuration
file had \pdfpagewidth and \pdfpageheight set to
210 mm and 297 mm instead of 210 truemm and 297 truemm.
However, pdftexconfig.tex does have true dimensions, as
it should.

It seems to me that there must be some bug. Can anyone
shed any light on this for me?

Bob Howlett