Can I install sudo/su with the signed apk exploit?
The Exploit (&amp; Fix) Android "Master Key" article describes the process of using the “Master Key” exploit to get elevated privileges with lots of technical details. The main point is that the exploit by itself does not give root privileges — only arbitrary code execution as the system user, and another privilege elevation exploit is needed to get root privileges (one well-known example shown in the article is writing ro.kernel.qemu=1 to /data/local.prop, but this attack is blocked in most Android 4.1 and later versions).

The article also provides download links for the Cydia Impactor tool which automates the “Master Key” exploit (currently only up to getting the system user rights, not all the way to root). There are versions for Windows and Mac OS X.