Security researcher Arminius has discovered a hackable vulnerability and exploit in Vim, arguably the most commonly used text editor among developers, hackers, and system engineers.
Vim is generally included as "vi" in most Unix and MacOS distributions. The vulnerability takes advantage of a vim feature called modeline, which is typically used to create custom settings for the way text or formatting will be handled in a file, for a project, or for all occasions of the editor's use.
In the exploit, a particular text string can be entered that causes the editor to accept arbitrary code and execute it outside of the sandbox in which most modeline commands are executed, regardless of whether that code has anything to do with the editor. The exploit is possible because, in many implementations, modeline is enabled by default, regardless of whether the system owner is using the feature.
The vulnerability has been patched in Vim patch 8.1.1365 and a Neovim patch (released in v0.3.6), but Arminius recommends that users explicitly disable modeline on their systems.