Difference between revisions of "UnsafeWindow"

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(Basic unsafeWindow setup.)
 
 
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{{title=unsafeWindow}}
{{DISPLAYTITLE:unsafeWindow}}
{{security}}


= Syntax =
== Description ==


'''unsafeWindow'''
This [object allows a [[User script]] to access "custom" properties set by the web page.
The user script is otherwise isolated from these properties.


= Description =
:*'''USE OF UNSAFEWINDOW IS INSECURE, AND IT SHOULD BE AVOIDED WHENEVER POSSIBLE.'''


Userscripts can use this object to access document functions, variables and other elements in the document. unsafeWindow is a object wrapper for the entire document object.
unsafeWindow bypasses [[Greasemonkey]]'s security model, which exists to make sure that malicious web pages cannot alter objects in such a way as to make user scripts (which execute with more privileges than ordinary JavaScript running in a web page) do things that their authors or users did not intend.
User scripts should therefore avoid calling or in any other way depending on any properties on unsafeWindow - especially if they are executed for arbitrary web pages, such as those with <code>@[[Include and exclude rules|include]] *</code>..


= Examples =
== Examples ==


unsafeWindow.document.title="Testing"
<pre class='sample-bad'>
unsafeWindow.TestVarCreatedByDocument="Testing"
unsafeWindow.SomeVarInPage = "Testing";
unsafeWindow.document.TestFunction("Test")
</pre>
 
<pre class='sample-bad'>
unsafeWindow.SomeFunctionInPage("Test");
</pre>
 
<pre class='sample-bad'>
var oldFunction = unsafeWindow.SomeFunctionInPage;
unsafeWindow.SomeFunctionInPage = function(text) {
  alert('Hijacked! Argument was ' + text + '.');
  return oldFunction(text);
};
</pre>
 
== Alternatives to unsafeWindow ==
 
''Sometimes'', you just can't get around using unsafeWindow.
Most of the time, however, you can!
See [[:Category:Coding Tips:Interacting With The Page]] for details on various methods to interact with the page that do '''not''' use unsafeWindow.
 
[[Category:API_Reference|U]]
[[Category:Scripting context]]
[[Category:Security]]

Latest revision as of 15:17, 3 November 2017

This command can open certain security holes in your user script, and it is recommended to use this command sparingly.

Please be sure to read the entire article and understand it before using it in a script.


Description

This [object allows a User script to access "custom" properties set by the web page. The user script is otherwise isolated from these properties.

  • USE OF UNSAFEWINDOW IS INSECURE, AND IT SHOULD BE AVOIDED WHENEVER POSSIBLE.

unsafeWindow bypasses Greasemonkey's security model, which exists to make sure that malicious web pages cannot alter objects in such a way as to make user scripts (which execute with more privileges than ordinary JavaScript running in a web page) do things that their authors or users did not intend. User scripts should therefore avoid calling or in any other way depending on any properties on unsafeWindow - especially if they are executed for arbitrary web pages, such as those with @include *..

Examples

unsafeWindow.SomeVarInPage = "Testing";
unsafeWindow.SomeFunctionInPage("Test");
var oldFunction = unsafeWindow.SomeFunctionInPage;
unsafeWindow.SomeFunctionInPage = function(text) {
  alert('Hijacked! Argument was ' + text + '.');
  return oldFunction(text);
};

Alternatives to unsafeWindow

Sometimes, you just can't get around using unsafeWindow. Most of the time, however, you can! See Category:Coding Tips:Interacting With The Page for details on various methods to interact with the page that do not use unsafeWindow.