Even after Oracle patched critical Java vulnerabilities on Monday US time, the US Computer Emergency Readiness Team (US-CERT) continued urging users to disable Java browser plug-ins.
"Due to the number and severity of this and prior Java vulnerabilities, it is recommended that Java be disabled temporarily in web browsers," said US-CERT in a note on Monday, a day after Oracle shipped an "out-of-band," or emergency update.
While calls to disable a plug-in - or even to stop using a particular browser - are not uncommon in the face of active exploits of an unpatched vulnerability, it's unusual that they continue after a patch is released.
But a pair of security professionals, including a researcher known for uncovering scores of Java bugs, said US-CERT's move was justified.
"Disabling Java seems to be a reasonable step to mitigate the risk associated with confirmed, not-yet-patched flaws," said Adam Gowdiak, founder and CEO of Security Explorations, in an email late Tuesday.
Gowdiak was referring to other Java vulnerabilities he has reported to Oracle, including two that he has been told will be patched in an upcoming February 19 update.
Andy Chou, CTO of Coverity, a San Francisco-based developer whose products scan other software for potential security flaws, agreed with Gowdiak.
"Most users don't need to visit sites that use Java applets," said Chou in an email interview. "For them Java is just dead code. [So] it seems reasonable for many users to turn off a feature they don't need."
Recommendations from US-CERT, which is part of the US Department of Homeland Security, carry special weight: The organisation acts as a threat clearinghouse and security coordinator for both the public and private sectors.
Gowdiak noted that US-CERT could be basing its recommendation not only on publicly-available information, but also on confidential government sources.
Disabling the Java plug-in inside browsers may be the solution for many, as Chou argued, but some - enterprise workers especially, but not exclusively - rely on Java web applets.
So what's their move?
Gowdiak and Chou each recommended that users run Firefox or Chrome, both of which provide a feature dubbed "click-to-play" that requires the user to explicitly authorise a plug-in's execution.
In Chrome, the setting is under the advanced section of Settings (Windows) or Preferences (OS X), in the Privacy subsection. Users must click the "Content Settings" button, then scroll to view the "Plug-ins" listing.
"Those needing the Java plug-in on a daily basis might think about adopting some form of click-to-play technology that would allow for a flexible configuration of the conditions under which the plug-in is allowed to run in the browser," said Gowdiak.
Java 7, the version exploitable through the latest vulnerabilities, has an option that lets users completely disable the plug-in. Sunday's update also modified Java's security settings so that it now refuses to run unsigned applets without user approval.
Chou urged users to be cautious while browsing potentially-risky sites, although that may be difficult: Exploits are often hosted on legitimate websites that have been compromised by hackers.
Java has been increasingly targeted by attackers, in part because it's a cross-platform technology that can be exploited not only on Windows PCs, but also on Macs. According to the Russian antivirus vendor Kaspersky, more than half of all attacks in the third quarter of 2012 leveraged Java vulnerabilities. Microsoft said much the same more than a year ago.
Other companies' software has been similarly targeted in the past, notably Adobe's Reader, a factor in that firm's increased attention to security over the last few years. Oracle may need to do the same to prove that Java is secure enough to use.
"This is a wake-up call for [Oracle]," said Gowdiak, when asked whether the US-CERT recommendation had long-term implications for Java's survival and continued use.
"This isn't the demise of Java," cautioned Chou. "It won't be going away anytime soon, especially on the server side and for desktop applications. I have no idea if Oracle will be able to move Java onto a more secure path. [But] it takes time, even when the organisation is serious."
Other security pros, though, were ready to give up on Java. In a tweet last week, Andrew Storms, director of security operations at nCircle Security, simply said, "Just uninstall Java."