Adobe: JSX and JSXBIN files

September 2, 2022 in Autostart (Persistence), EDR, Incident Response

I wrote about older Adobe scripting before. I recently discovered that Adobe products support scripting using so-called ExtendScript language with code being stored either in a source-level JSX file, or its binary equivalent – JSXBIN (it’s actually considered legacy at this stage). Add these file extensions to your watch list.

The documentation [PDF warning] suggests that some security precautions are in place, and:

1.5 Activating full scripting features
The default is for scripts to not be allowed to write files or send or receive communication over a network. To allow
scripts to write files and communicate over a network, choose Edit > Preferences > General (Windows) or After Effects Preferences > General (Mac OS), and select the Allow Scripts To Write Files And Access Network option.
Any After Effects script that contains an error preventing it from being completed generates an error message from the application. This error message includes information about the nature of the error and the line of the script on which it occurred. The ExtendScript Toolkit (ESTK) debugger can open automatically when the application encounters a script error. This feature is disabled by default so that casual users do not encounter it. To activate this feature, choose Preferences > General, and select Enable JavaScript Debugger

I don’t have access to Adobe products, but these seem to be interesting features.

Defenders should look for:

  • unusual processes spawn by Adobe products
  • invocations of afterfx.exe – scrutinize its command line
  • on macOS: use of AppleScript to invoke DoScript
  • presence/invocation of autostart scripts in Adobe’s Startup and Shutdown folders (the exact location is unknown to me; if you have Adobe products, please let me know and I will update this post)

1.6.5 Running scripts automatically during application startup or shutdown
Within the Scripts folder are two folders called Startup and Shutdown. After Effects runs scripts in these folders
automatically, in alphabetical order, on starting and quitting, respectively

Yes, it’s not a lot to pivot from, but if you have an access to a large number of systems, you may want to keep an eye on process trees spawn around Adobe products. Just to be ahead of time.

Other info:

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