libxslt - security update

Nick Wellnhofer discovered that the xsltFormatNumberConversion function
in libxslt, an XSLT processing runtime library, does not properly check
for a zero byte terminating the pattern string. This flaw can be
exploited to leak a couple of bytes after the buffer that holds the
pattern string.

For the stable distribution (jessie), this problem has been fixed in
version 1.1.28-2+deb8u2.

For the testing distribution (stretch), this problem has been fixed
in version 1.1.29-2.

For the unstable distribution (sid), this problem has been fixed in
version 1.1.29-2.

We recommend that you upgrade your libxslt packages.