Mozilla Foundation Security Advisory 2015-122
Trailing whitespace in IP address hostnames can bypass same-origin policy
- November 3, 2015
- Michał Bentkowski
- Firefox, Firefox ESR, Thunderbird
- Fixed in
- Firefox 42
- Firefox ESR 38.4
- Thunderbird 38.4
Security researcher Michał Bentkowski reported that adding white-space characters to hostnames that are IP addresses can bypass same-origin policy. This flaw was caused by trailing whitespaces being evaluated differently when parsing IP addresses instead of alphanumeric hostnames. This could lead to a cross-site script (XSS) attack.
In general this flaw cannot be exploited through email in the Thunderbird product because scripting is disabled, but is potentially a risk in browser or browser-like contexts.