Leveraging JavaScript Injection

[3LineLarry]

I am hacking a smart device and have found a JavaScript injection vulnerability and need advice or new ideas on how to leverage it into an active shell session or how to enumerate it further. I already have access to the basic file system and have enumerated lots of info on it. I am in need of malicious JavaScript code that can bypass a sand boxed browser and help obtain a shell or download a malicious apk. Any ideas to help run malicious JavaScript code to enumerate the device or elevate privileges on the filesystem or really any new ideas would be heavily appreciated! Thanks!!