<script> elements, but also things like inline script event handlers (
onclick) and XSLT stylesheets which can trigger script execution.
|Directive type||Fetch directive|
Yes. If this directive is absent, the user agent will look for the
One or more sources can be allowed for the
Content-Security-Policy: script-src <source>; Content-Security-Policy: script-src <source> <source>;
Internet hosts by name or IP address, as well as an optional URL scheme and/or port number. The site's address may include an optional leading wildcard (the asterisk character,
'*'), and you may use a wildcard (again,
'*') as the port number, indicating that all legal ports are valid for the source. Examples:
http://*.example.com: Matches all attempts to load from any subdomain of example.com using the
mail.example.com:443: Matches all attempts to access port 443 on mail.example.com.
https://store.example.com: Matches all attempts to access store.example.com using
*.example.com: Matches all attempts to load from any subdomain of example.com using the current protocol.
A scheme such as
https:. The colon is required. Unlike other values below, single quotes shouldn't be used. You can also specify data schemes (not recommended).
data:URIs to be used as a content source. This is insecure; an attacker can also inject arbitrary data: URIs. Use this sparingly and definitely not for scripts.
mediastream:URIs to be used as a content source.
blob:URIs to be used as a content source.
filesystem:URIs to be used as a content source.
Refers to the origin from which the protected document is being served, including the same URL scheme and port number. You must include the single quotes. Some browsers specifically exclude
filesystemfrom source directives. Sites needing to allow these content types can specify them using the Data attribute.
Allows the use of
eval()and similar methods for creating code from strings. You must include the single quotes.
Allows enabling specific inline event handlers. If you only need to allow inline event handlers and not inline
For every inline event-handler attribute in the document, you must generate a hash from the value of the attribute (that is, the complete code in the attribute’s value), using a particular hash algorithm (e.g.,
sha512), and then add a
<hash-algorithm>-<base64-value>source expression for that hash to the value of the
Allows the use of inline resources, such as inline
Refers to the empty set; that is, no URLs match. The single quotes are required.
An allow-list for specific inline scripts using a cryptographic nonce (number used once). The server must generate a unique nonce value each time it transmits a policy. It is critical to provide an unguessable nonce, as bypassing a resource's policy is otherwise trivial. See unsafe inline script for an example. Specifying nonce makes a modern browser ignore
'unsafe-inline'which could still be set for older browsers without nonce support.
Note: The CSP
noncesource can only be applied to nonceable elements (e.g., as the
<img>element has no
nonceattribute, there is no way to associate it with this CSP source).
A sha256, sha384 or sha512 hash of scripts or styles. The use of this source consists of two portions separated by a dash: the encryption algorithm used to create the hash and the base64-encoded hash of the script or style. When generating the hash, don't include the <script> or <style> tags and note that capitalization and whitespace matter, including leading or trailing whitespace. See unsafe inline script for an example. In CSP 2.0, this is applied only to inline scripts. CSP 3.0 allows it in the case of
script-srcfor external scripts.
strict-dynamicsource expression specifies that the trust explicitly given to a script present in the markup, by accompanying it with a nonce or a hash, shall be propagated to all the scripts loaded by that root script. At the same time, any allow-list or source expressions such as
Requires a sample of the violating code to be included in the violation report.
Given this CSP header:
Content-Security-Policy: script-src https://example.com/
the following script is blocked and won't be loaded or executed:
Note that inline event handlers are blocked as well:
<button id="btn" onclick="doSomething()">
You should replace them with
Note: Disallowing inline styles and inline scripts is one of the biggest security wins CSP provides. However, if you absolutely have to use it, there are a few mechanisms that will allow them.
To allow inline scripts and inline event handlers,
'unsafe-inline', a nonce-source or a hash-source that matches the inline block can be specified.
Content-Security-Policy: script-src 'unsafe-inline';
The above Content Security Policy will allow inline
<script> var inline = 1; </script>
You can use a nonce-source to only allow specific inline script blocks:
Content-Security-Policy: script-src 'nonce-2726c7f26c'
You will have to set the same nonce on the
<script nonce="2726c7f26c"> var inline = 1; </script>
Alternatively, you can create hashes from your inline scripts. CSP supports sha256, sha384 and sha512.
Content-Security-Policy: script-src 'sha256-B2yPHKaXnvFWtRChIbabYmUBFZdVfKKXHbWtWidDVF8='
When generating the hash, don't include the
<script> tags and note that capitalization and whitespace matter, including leading or trailing whitespace.
<script>var inline = 1;</script>
'unsafe-eval' source expression controls several script execution methods that create code from strings. If
'unsafe-eval' isn't specified with the
script-src directive, the following methods are blocked and won't have any effect:
'strict-dynamic' source expression specifies that the trust explicitly given to a script present in the markup, by accompanying it with a nonce or a hash, shall be propagated to all the scripts loaded by that root script. At the same time, any allowlist or source expressions such as
'unsafe-inline' will be ignored. For example, a policy such as
script-src 'strict-dynamic' 'nonce-R4nd0m' https://allowlisted.example.com/ would allow loading of a root script with
<script nonce="R4nd0m" src="https://example.com/loader.js"> and propagate that trust to any script loaded by
loader.js, but disallow loading scripts from
https://allowlisted.example.com/ unless accompanied by a nonce or loaded from a trusted script.
Content-Security-Policy: script-src 'strict-dynamic' 'nonce-someNonce'
Content-Security-Policy: script-src 'strict-dynamic' 'sha256-base64EncodedHash'
It is possible to deploy
strict-dynamic in a backwards compatible way, without requiring user-agent sniffing.
Content-Security-Policy: script-src 'unsafe-inline' https: 'nonce-abcdefg' 'strict-dynamic'
will act like
'unsafe-inline' https: in browsers that support CSP1,
https: 'nonce-abcdefg' in browsers that support CSP2, and
'nonce-abcdefg' 'strict-dynamic' in browsers that support CSP3.
|Content Security Policy Level 3 (Content Security Policy 3)|
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