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.
Users should refrain from accepting and executing files that originate from unknown or untrusted sources.
Implement multiple redundant layers of security.
Since this issue may be leveraged to execute code, we recommend memory-protection schemes, such as nonexecutable stack/heap configurations and randomly mapped memory segments. This tactic may complicate exploits of memory-corruption vulnerabilities.
Microsoft released an advisory and fixes to address this issue. Please see the references for more information.