The remote host is missing an update to xterm announced via advisory DSA 1694-2.

https://secure1.securityspace.com/smysecure/catid.html?in=DSA%201694-2

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. For the stable distribution (etch), this problem has been fixed in version 222-1etch4. For the testing distribution (lenny), this problem has been fixed in version 235-2. For the unstable distribution (sid), this problem has been fixed in version 238-2. We recommend that you upgrade your xterm package.