Debian Security Advisory 1694-2 – The xterm update in DSA-1694-1 disabled font changing as a precaution. However, users reported that they need this feature. The update in this DSA makes font shifting through escape sequences configurable, using a new allowFontOps X resource, and unconditionally enables font changing through keyboard sequences.
You can download this advisory from the following link: https://packetstormsecurity.com/files/download/73638/dsa-1694-2.txt
Source: https://packetstormsecurity.com/files/73638/Debian-Linux-Security-Advisory-1694-2.html