diff --git a/common/app/routes/Challenges/rechallenge/builders.js b/common/app/routes/Challenges/rechallenge/builders.js
index e076440383..3984c83e0d 100644
--- a/common/app/routes/Challenges/rechallenge/builders.js
+++ b/common/app/routes/Challenges/rechallenge/builders.js
@@ -19,6 +19,20 @@ import {
const htmlCatch = '\n\n';
const jsCatch = '\n;/*fcc*/\n';
+const loopProtector = `
+ window.loopProtect = parent.loopProtect;
+ window.__err = null;
+ window.loopProtect.hit = function(line) {
+ window.__err = new Error(
+ 'Potential infinite loop at line ' +
+ line +
+ '. To disable loop protection, write:' +
+ ' // noprotect as the first' +
+ ' line. Beware that if you do have an infinite loop in your code' +
+ ' this will crash your browser.'
+ );
+ };
+`;
const defaultTemplate = ({ source }) => `
@@ -28,7 +42,7 @@ const defaultTemplate = ({ source }) => `
`;
const wrapInScript = partial(transformContents, (content) => (
- `${htmlCatch}`
+ `${htmlCatch}`
));
const wrapInStyle = partial(transformContents, (content) => (
`${htmlCatch}`