Active rule currently in use.
Atomicorp.com WAF Rules: Hidden Text Detected
This rules detects patterns commonly used by web spammers and malware. This by itself may not be an attack.
Specifically this rule detects the use of content markup methods that "hide" the content. For example, methods that make text hidden (but is still loaded by a web browser), or that make sections of a page invisible but potentially still visible to a search engine of browser.
A false positive can occur when a website legitimately uses this type of content, or if there is an error in the patterns used to detect this. The rules contain a large library of known web applications and safe methods for using this content, such as administrative functions, and can detect known safe methods and ignore them. However it is possible for a new or custom application to do this in an unknown manner and incorrectly trigger this rule.
It is not recommended that you disable this rule if you have a false positive. If you believe this is a false positive, please report this to our security team to determine if this is a legitimate case, or if its clever attack on your system. Instructions to report false positives are detailed on the Reporting False Positives wiki page. If it is a false positive, we will fix the issue in the rules and get a release out to you promptly.
If you know that this behavior is acceptable for your application, you can tune it by by following the guidance in the Tuning the Atomicorp WAF Rules page.