Simple, clean server resource pack "Exploit" fix.

No external dependencies besides Forge.
The "Exploit" ONLY allows for the server to check if a file exists on the client or not.
And as a side effect cause the game to try and load the file as a resource pack.
There are currently no know issues with java's zip file management that would allow for any extra malicious activity.
So any claims of people being able to steal your passwords/execute code/etc.. is unfounded. Hence the name RedHerring.

For more info refer to: https://ungeek.eu/minecraft-18-file-access/ Ignore the fear mongering bits like:
"Servers can check if a file exists on the player's computer, enumerate users names but maybe even worse. See PHP's issue with file_exists and phar files."

Logo Found at TvTrops, CC-BY-SA-4.0, https://commons.wikimedia.org/wiki/File:Redherring.gif