content.js

var clickedEl = null;

// Listen for messages
chrome.runtime.onMessage.addListener(function (msg, sender, sendResponse) {
    // If the received message has the expected format...
    if (msg.text === 'report_back') {
        // Call the specified callback, passing
        // the web-page's DOM content as argument
        sendResponse(clickedEl);
    }
});

document.addEventListener("mousedown", function(event){
    //right click
    if(event.which === 3) {
        clickedEl = $(event.target).closest("[id^='issue']").attr('id');
    }
});