Google Groups File Attachment Restrictions Bypassed via Email Posting

A significant security vulnerability has been identified in Google Groups, allowing users to circumvent file attachment restrictions by simply sending emails to group addresses. 

This broken access control issue potentially impacts thousands of organizations that rely on Google Groups for controlled information sharing and collaboration.

Ph.Hitachi recently observed the vulnerability, which exploits a disconnect between two Google Groups features: attachment permissions and email posting capabilities.

Google Groups Attachment Bypass Vulnerability

According to the technical report, even when group administrators explicitly restrict file upload permissions to “owners only,” regular members can bypass this restriction by sending an email with attachments to the group’s email address.

The “Allow Email Posting” setting is at the core of this vulnerability. This setting enables members to contribute to discussions by sending emails directly to the group’s address (typically formatted as groupname@googlegroups.com). 

While this feature facilitates easier participation, it fails to enforce the attachment restrictions configured in the group’s settings.

The report notes that the attachment should be blocked if the group setting specifies that only owners can add files. It highlights the expected behavior versus the actual outcome, where the attachment is successfully posted despite the restriction.

The reproduction steps for this vulnerability are straightforward:

• Create a Google Group with restricted attachment permissions
• Enable the “Allow Email Posting” setting for group members
• As a regular member, send an email with an attachment to the group address
• Observe that the attachment is successfully posted despite restrictions

This vulnerability represents a classic broken access control issue where permission checks are inconsistently applied across different access methods to the same resource.

This vulnerability could have significant consequences for enterprises and organizations using Google Groups for sensitive communications. 

According to recent research, over 9,600 organizations have already experienced data leaks due to misconfigured Google Groups settings. This newly discovered bypass method further complicates security governance for Google Workspace administrators.

Security experts recommend implementing comprehensive access controls and practicing proper data categorization to limit exposure to confidential information.

This discovery highlights the ongoing challenges in maintaining consistent security controls across interconnected features in cloud-based collaboration platforms, even for industry leaders like Google.

For Google Workspace administrators, it emphasizes the importance of regularly reviewing group configurations and understanding the potential security implications of seemingly helpful features like email posting.

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The post Google Groups File Attachment Restrictions Bypassed via Email Posting appeared first on Cyber Security News.