You're looking for a free download of XMult, a plugin for Adobe After Effects. Here's what I found:
It creates a clean alpha channel based on the highest luminance value of each pixel while compensating the RGB channels to prevent "black fringing". How to Install XMult in After Effects xmult after effects free download
Extracting foreground objects like fireworks, smoke, or muzzle flashes filmed against black. Key Advantage: You're looking for a free download of XMult,
A: No. Portable plugins don’t exist for AE. Any “portable XMult” is a virus. xmult after effects free download