Historical security notice: the incident and temporary workaround below relate to Internet Explorer in September 2012. Do not treat the old workaround as current protection. Use a supported browser and your organisation’s current security guidance.
On 18th September 2012, Microsoft released a temporary fix for a discovered software vulnerability. The security flaw in question allows the Poison Ivy Trojan to be installed on its browsers – and according to Microsoft’s website, nearly all versions are affected. This malware is capable of stealing data and taking remote control of PC’s, so it’s important to act fast.
If you’re an Internet Explorer user, the advice is to swap to another browser until a permanent software update is available (which should be in around a week).
Alternatively, you can try a workaround as a temporary fix – instructions are on their blog post https://technet.microsoft.com/en-us/security/advisory/2757760 (note: link removed due to redirects). This workaround, however, is for advanced users only.