Simon Willison’s Weblog

Items tagged security, recovered

Filters: security × recovered ×


CSRF: Flash + 307 redirect = Game Over. Here’s the exploit that Django and Rails both just released fixes for. It’s actually a flaw in the Flash player. Flash isn’t meant to be able to make cross-domain HTTP requests with custom HTTP headers unless the crossdomain.xml file on the other domain allows them to, but it turns out a 307 redirect (like a 302, but allows POST data to be forwarded) confuses the Flash player in to not checking the crossdomain.xml on the host it is being redirect to. # 10th February 2011, 10:07 pm

The code injected to steal passwords in Tunisia. Here’s the JavaScript that (presumably) the Tunisian government were injecting in to login pages that were served over HTTP. # 24th January 2011, 6:45 pm

National politics of snoopiness vs corporate ethic of not being evil aren’t directly compatible, and the solution here only works because (let’s face it) Tunisia is not a rising economic force. If you’re selling ads in China, you don’t get to pretend that the Great Firewall of China is a security issue.

Nat Torkington # 24th January 2011, 6:11 pm

The Inside Story of How Facebook Responded to Tunisian Hacks (via) “By January 5, it was clear that an entire country’s worth of passwords were in the process of being stolen right in the midst of the greatest political upheaval in two decades.”—which is why you shouldn’t serve your login form over HTTP even though it POSTs over HTTPS. # 24th January 2011, 6:06 pm

Bleach, HTML sanitizer and auto-linker. HTML sanitisation is notoriously difficult to do correctly, but Bleach (a Python library) looks like an excellent effort. It uses the html5lib parsing library to deal with potentially malformed HTML, uses a whitelist rather than a blacklist and has a neat feature for auto-linking URLs that is aware of the DOM (so it won’t try to auto-link a URL that is already wrapped in a link element). It was written by the Mozilla team for addons.mozilla.org and support.mozilla.org so it should be production ready. # 25th October 2010, 1:32 pm

Firesheep (via) Oh wow. A Firefox extension that makes sniffing for insecured (non-HTTPS) cookie requests on your current WiFi network and logging in as that person a case of clicking a couple of buttons. Always possible of course, but it’s never been made easy before. Private VPNs are about to become a lot more popular. # 25th October 2010, 9:11 am

Schneier on Stuxnet. Stuxnet now rivals Wikileaks as the real life plot most likely to have leaked from science fiction. # 9th October 2010, 10:57 am

Jeremiah Grossman: I know who your name, where you work, and live. Appalling unfixed vulnerability in Safari 4 and 5 —if you have the “AutoFill web forms using info from my Address Book card” feature enabled (it’s on by default) malicious JavaScript on any site can steal your name, company, state and e-mail address—and would be able to get your phone number too if there wasn’t a bug involving strings that start with a number. The temporary fix is to disable that preference. # 22nd July 2010, 8:44 am

“Likejacking” Takes Off on Facebook. The Facebook Like button is vulnerable to Clickjacking, and is being widely exploited. Since Likes show up in your Facebook stream, it’s an easy attack to make viral. The button is implemented on third party sites as an iframe, which would seem to me to be exploitable by design (just make the iframe transparent in the parent document and trick the user in to clicking in the right place). I can’t think of any way they could support the embedded Like button without being vulnerable to clickjacking, since clickjacking prevention relies on not allowing your UI elements to be embedded in a hostile site while the Like button’s functionality depends on exactly that. # 3rd June 2010, 10:01 am

A New Type of Phishing Attack. Nasty trick from Ava Raskin—detect when your evil phishing page loses focus (when the user switches to another tab, for example), then replace the page content with a phishing UI from a site such as Gmail. When the user switches back they’re much less likely to bother checking the URL. Combine with CSS history sniffing to only show a UI for a site that you know the user has visited. Combine that with timing tricks to only attack sites which the user is currently logged in to. # 25th May 2010, 3:20 pm

OpenCart CSRF Vulnerability. Avoid OpenCart—it’s vulnerable to CSRF, but the maintainer has no intention of fixing it as “there is no way that I’m responsible for a client being stupid enough to click links in emails”. # 25th May 2010, 12 am

Busting frame busting: a study of clickjacking vulnerabilities at popular sites (via) Fascinating and highly readable security paper from the Stanford Web Security Research group. Clickjacking can be mitigated using framebusting techniques, but it turns out that almost all of those techniques can be broken in various ways. Fun examples include double-nesting iframes so that the framebusting script overwrites the top-level frame rather than the whole window, and a devious attack against the IE and Chrome XSS filters which tricks them in to deleting the framebusting JavaScript by reflecting portions of it in the framed page’s URL. The authors suggest a new framebusting snippet that should be more effective, but sadly it relies on blanking out the whole page in CSS and making it visible again in JavaScript, making it inaccessible to browsers with JavaScript disabled. # 24th May 2010, 11:40 am

The answers to your Security Questions are case sensitive and cannot contain special characters like an apostrophe, or the words “insert,” “delete,” “drop,” “update,” “null,” or “select.”

Sacramento Credit Union # 14th May 2010, 12:40 am

When Ajax Attacks! Web application security fundamentals. Slides and (other people’s) notes from my presentation at @media Ajax on Tuesday. # 17th September 2008, 11:18 pm