Note: FT disabled the app so you cannot read the news for free anymore. You can still access the archived versions though, with the link provided at the end of this article. This incident happened back in August 2018.

I once stumbled upon an article from Financial Times, an online newspaper with emphasis on business and economic news.

The article, named What happens when you visit, describes what happens in the background when one makes a request to Besides many interesting technical details, I noted that FT used Heroku for hosting its services.

If you have ever used Heroku, you know that apps get public <NAME> domain by default. For example, say I register a Heroku app and name it apple. When I deploy my apple app (e.g., a RESTful web server), I will be able to access it on

The moment I saw a word Heroku in their article, I wondered if I could randomly guess any of their services’ URL. Out of curiosity, I tried a few. Surprisingly, one of the URLs (namely, worked; I managed to access the same contents as in What was more exciting is that I could access paid articles for free. In other words, one could read all articles, paid or not, without any subscription whatsoever.

Being not sure how serious this issue is, I nevertheless hoped to get some bounty for finding out a “backdoor” that let anyone read paid articles for free (in other words, authorization could be bypassed). After reporting the issue, even though I got nothing back (*sigh*), the URL link now does not render any FT content and the issue seem to be resolved.

It may have happened that one or more engineering staff members forgot to remove that app. Who knows, maybe it was used for testing (e.g., black-box system testing) or something else.

P.S. You can access archived versions of the website from 2017 at