It has a little different behaviour compared to IE8 XSS filter, in fact with this filter an attacker could deactivate a “script” by passing its code in a request parameter. This enables the framing page to specifically target a single snippet containing the frame busting code, leaving all the other codes intact. Attacker View:
<iframe src=”http://target site/?param=if(top+!%3D+self)+%7B+top.location%3Dself.location%3B+%7D”>Source: Clickjacking/README.md in PayloadsAllTheThings. From PayloadsAllTheThings by Swissky and contributors. MIT License, Copyright (c) 2019 Swissky.