An open(ish) redirect on Mastodon

Cartoon of a tusked mastodon holding a phone.

I've responsibly disclosed a small security issue with Mastodon (GHSA-8982-p7pm-7mqw). It allows a sufficiently determined attacker to use any Mastodon instance to redirect unwary users to a malicious site. What do you think happens if you visit: If you aren't logged in to that instance, it will redirect you to a 3rd party site. […]

Continue reading →

Responsible Disclosure: arXiv - redirect on login

A padlock engraved into a circuit board.

Suppose you are sent a link to a website - e.g. But, before you can access it, you need to log in. So the website redirects you to: If you get the password right, you go to the original page you requested. Nice! But what happens if someone manipulates that query string? Suppose […]

Continue reading →

Responsible Disclosure: Abandoned Buckets and Billing Emails

Error saying the bucket does not exit.

A few weeks ago, I received a billing email from my phone provider O21. While glancing at it, I noticed all the images were broken. Viewing the source of the email showed that they were all coming from http:// What happens if we visit that domain? Ah, the dreaded "The specified bucket does not […]

Continue reading →

Responsible Disclosure: XSS in Codeberg Pages

An XSS pop up alert on a webpage.

Codeberg is a hip new code hosting site - similar to GitHub and GitLab. And, much like Gits Hub & Lab, users can serve static content through Codeberg pages. Somehow I screwed up my configuration, and when I visited I got this error: Now, whenever I see something from the request echoed into the […]

Continue reading →

What's the most malicious thing you can do with an injected HTML heading element?

The HTML5 Logo.

A bit of a thought experiment - similar to my Minimum Viable XSS and SVG injection investigations. I recently found a popular website which echoed back user input. It correctly sanitised < to &lt; to prevent any HTML injection. Except… It let through <h2> elements unaltered! Why? I suspect because the output was: <h2>Your search […]

Continue reading →

Responsible Disclosure: An Exam Board Touting Dodgy PDFs

Screenshot of some Javascript embedded in a page.

I hate academic tests. Wouldn't it be great if you could find the official answer papers? Oh, cool, the OCR Exam Board is hosting answer sheets for all my classes! What happens if I click it? Yeach! It redirects users to a scammy ebook service hosted on an external website. Which, I assume, the exam […]

Continue reading →

Responsible Disclosure: Chrome security bug let tabs draw over each other ($1k bounty)

The Google Logo.

Chrome for Android had a flaw which let one tab draw over another - even if the tabs were on completely different domains. A determined attacker might have been able to abuse this to convince a user to download and installed a spoofed app. See Chrome Bug #1242315 for details. Demo Here's a video of […]

Continue reading →

Full Disclosure: XSS in Getty Images

Javascript popup on the Getty Images website.

I've spent two months trying to report this issue to Getty images. They haven't responded to my emails, phone calls, Tweets, or LinkedIn messages. I've tried escalating through OpenBugBounty and HackerOne - but still no response. I've taken the decision to fully disclose this XSS because the Getty Images sites accept payments from users - […]

Continue reading →

Responsible Disclosure: [REDACTED] XSS

A pop-up on a website. The HTML code shows the data has been injected.

Legacy websites are a constant source of vulnerabilities. In a fit of excitement, a team commissions a service and then never bothers updating it. Quite often the original owners leave the business and there's no-one left who remembers that the service exists. So it sits there, vulnerable, for years. The [REDACTED] website had a subdomain […]

Continue reading →

Responsible Disclosure - John Lewis

John Lewis Website with a big circle drawn on it.

The HTML5 specification is complicated. I've been an author on it, and even I couldn't tell you all the weird little gotchas it contains. Between that and "idiosyncratic" browser engines, it's a wonder the world wide web works at all. Let's talk about the humble <meta> element. As its name suggests, it contains metadata about […]

Continue reading →