Microsoft Excel is prone to a remote code-execution vulnerability. Attackers could exploit this issue by enticing victims to open a maliciously crafted Excel file. Successful exploits will allow attackers to execute arbitrary code with the privileges of the user running the application.
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.
The vendor has released an update. Please see the references for details.