Technical Tip: Website Content Not Loading Fully with FortiWeb Signature Rule

Description

This article describes an issue where certain website content fails to load completely after enabling a Signature Rule category in a Web Protection Profile on FortiWeb.

Scope

FortiWeb.

FortiWeb versions prior to v8.0.5.

Solution

Issue: 

After attaching a Signature Rule category to a Web Protection Profile, the website may not load completely.
Users may observe that some page elements fail to render or that the browser receives an incomplete HTTP response.

Environment variable:

Server uses zstd content compression.

This issue occurs due to a defect in FortiWeb's handling of zstd-compressed HTTP responses. When Signature Rules inspect responses that are compressed using zstd, FortiWeb may fail to properly decompress the content, resulting in an incomplete response being sent to the client.

Possible workaround:

Disable Known Exploits, Trojan, Information Disclosure category in Signature profile.

This issue is resolved in FortiWeb 8.0.5.

1. Review the known issues and release notes for FortiWeb 8.0.5.

2. Back up the current configuration by navigating to System -> Maintenance -> Backup & Restore and downloading the configuration file.

3. Follow the recommended FortiWeb upgrade procedure.

4. Upgrade FortiWeb to version 8.0.5.

5. After the upgrade, re-enable the Signature Rule category and verify that the website loads successfully.

FortiWeb 8.0.5 Release Notes