CVE-2018-20167: Improper Neutralization of Special Elements in Output Used by a Downstream Component

Terminology before 1.3.1 allows Remote Code Execution because popmedia is mishandled, as demonstrated by an unsafe "cat README.md" command when \e}pn is used. A popmedia control sequence can allow the malicious execution of executable file formats registered in the X desktop share MIME types (/usr/share/applications). The control sequence defers unknown file types to the handle_unknown_media() function, which executes xdg-open against the filename specified in the sequence. The use of xdg-open for all unknown file types allows executable file formats with a registered shared MIME type to be executed. An attacker can achieve remote code execution by introducing an executable file and a plain text file containing the control sequence through a fake software project (e.g., in Git or a tarball). When the control sequence is rendered (such as with cat), the executable file will be run.