A one-click workaround is now available to protect against a zero-day vulnerability affecting version 8 of Internet Explorer (IE).
Microsoft announced that it has made a Fix-It available to address "known attacks that leverage the vulnerability to execute code," according to spokesman Dustin Childs. No restart is required.
Users running IE versions 6, 7, 9 and 10 do not need to take any action.
Microsoft disclosed the vulnerability over the weekend after reports emerged of a "watering hole" attack targeting a section of the US Department of Labor website, with the intended targets apparently being those who conduct nuclear weapons research.
No fewer than nine other sites also were clandestinely seeded with an exploit that takes advantage of the vulnerability.
Each of the affected sites are related to energy-related organisations, and researchers believe the malware campaign has been ongoing since mid-March.
It is unknown if Microsoft will have a full, working patch ready for this issue by Tuesday, when it is scheduled to distribute its monthly security update.