High Fidelity script to disable foot IK on your avatar.

disableFeetIK.js

var ikTypes = {
    RotationAndPosition: 0,
    RotationOnly: 1,
    HmdHead: 2,
    HipsRelativeRotationAndPosition: 3,
    Off: 4
};

function animStateHandler(props) {
    return { leftFootType: ikTypes["Off"],
             rightFootType: ikTypes["Off"] };
}

function init() {
    Script.update.connect(update);
    MyAvatar.addAnimationStateHandler(animStateHandler, ["leftFootType", "rightFootType"]);
}

function update(dt) {
    ;
}

function shutdown() {
    Script.update.disconnect(update);
    MyAvatar.removeAnimationStateHandler(animStateHandler);
}

Script.scriptEnding.connect(shutdown);

init();