My response to your earlier post:
BOO ... THIS IS FROM A YAHOO HELP PAGE ...
Some users have reported that their contacts received spam that originated from from their Yahoo! email account. This issue has been affecting multiple email providers with the spam containing a URL soliciting prescription medicine.
If you've experienced this issue, we strongly believe your account has been compromised and was used by an unauthorized third party to send spam or fraudulent emails to your contact list.
Please change your Password. By changing your password immediately, you quickly minimize the resulting risk for your Yahoo! account. For help selecting a strong password and/or safeguarding it against misuse, please review the tips posted in the password section of the Yahoo! Security Center.
We also suggest you perform a virus scan on your computer(s) if you haven't already done so.
Have you tried changing your password and running a virus scan?
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t.