Officials at the Mozilla Foundation on Friday acknowledged that a potentially dangerous code execution hole exists in fully patched versions of its flagship Firefox Web browser.
The open-source foundations confirmation comes on the same day it shipped Firefox 1.5 Beta 1 (code-named Deer Park) and highlights the delicate balancing act faced by Mozilla to market Firefox as a security upgrade over Microsofts dominant Internet Explorer.
The vulnerability, which was discovered and reported by independent security analyst Tom Ferris, affects all versions of Firefox (Windows and Linux), including the latest beta refresh.
In an advisory posted on Security-Protocols.com, Ferris described the bug as a buffer overflow that opens the door for an attacker to remotely execute arbitrary code on an affected host.
A proof-of-concept demonstration has also been published to show that a specially crafted URL can force Firefox to crash.
In some cases, a malicious hacker can exploit the buffer overflow to launch arbitrary code, either remotely or locally.
According to FrSIRT (French Security Incident Response Team), the flaw also affects the Mozilla suite.
"This flaw is due to a buffer overflow error in the "NormalizeIDN" function when handling specially crafted URLs embedded in HREF tags," FrSIRT said, warning that the vulnerability carries a "critical" rating.
A successful attacker could "take complete control of an affected system via specially crafted Web pages," FrSIRT added.
Security alerts aggregator Secunia Inc. also rated the issue as "highly critical" and recommended that Firefox users avoid browsing untrusted Web sites until a patch is released by Mozilla.
The issue was first reported to Mozilla on Sept. 4, and open-source volunteers have already created fixes for testing. A comprehensive patch will be released once quality assurance tests are complete.
The latest security hiccup is not the first that has sent Mozilla volunteers scrambling into damage-control mode.
Back in May, the foundation was forced to rush out a partial fix for a pair of "extremely critical" Firefox vulnerabilities after zero-day exploit code leaked onto the Internet.
Prior to that, Mozilla shipped a major security makeover to provide a temporary workaround for a widely reported IDN (International Domain Name) bug, and to correct two serious flaws that could allow malicious attackers to spoof the source displayed in the "Download Dialog" box or to spoof the content of Web sites.