Microsoft Excel is prone to a remote code-execution vulnerability. Attackers may exploit this issue by enticing victims into opening a maliciously crafted Excel file ('.xls'). Successful exploits may allow attackers to execute arbitrary code with the privileges of the user running the application. This may facilitate a compromise of vulnerable computers.
Run all software as a nonprivileged user with minimal access rights.
To reduce the impact of latent vulnerabilities, always run nonadministrative software as an unprivileged user with minimal access rights.
Do not accept or execute files from untrusted or unknown sources.
To reduce the likelihood of successful exploits, never handle files that originate from unfamiliar or untrusted sources.
Implement multiple redundant layers of security.
Memory-protection schemes (such as nonexecutable stack and heap configurations and randomly mapped memory segments) will complicate exploits of memory-corruption vulnerabilities.
Microsoft released fixes and an advisory to address this issue. Please see the references for more information. NOTE: On March 13, 2008, Microsoft updated security bulletin MS08-014. The vendor reported that some users may experience problems caused by this update. An issue in this update may lead to incorrect results from Excel calculations where a Real Time Data source is used in a user-defined Visual Basic for Applications function. Customers using Microsoft Excel 2003 Service Pack 2 or Service Pack 3 with a Real Time Data source for a user-defined Visual Basic for Applications function are advised to test additions before deploying this update. The vendor recommends considering the workarounds in security bulletin MS08-014 if this update cannot be deployed because of this issue.