Title

Read signed email as plain text must be enforced. (Cat II impact)

Discussion

Outlook can display email messages and other items in three formats: plain text, Rich Text Format (RTF), and HTML. By default, Outlook displays digitally signed email messages in the format which they were received.

Check Content

Verify the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Outlook Options >> Preferences >> E-mail Options "Read signed e-mail as plain text" is set to "Enabled". Procedure: Use the Windows Registry Editor to navigate to the following key: HKCU\Software\Policies\Microsoft\Office\16.0\outlook\options\mail Criteria: If the value ReadSignedAsPlain is REG_DWORD = 1, this is not a finding.

Fix Text

Set the policy value for User Configuration >> Administrative Templates >> Microsoft Outlook 2016 >> Outlook Options >> Preferences >> E-mail Options "Read signed e-mail as plain text" to "Enabled".

Additional Identifiers

Rule ID: SV-251865r811186_rule

Vulnerability ID: V-251865

Group Title: SRG-APP-000516

Expert Comments

CCIs tied to check.

Controls tied to check. These are derived from the CCIs shown above.