base-uri directive restricts the URLs which can be used in a document's
<base> element. If this value is absent, then any URI is allowed. If this directive is absent, the user agent will use the value in the
|Directive type||Document directive|
||No. Not setting this allows any URL.|
One or moresources can be allowed for the base-uri policy:
Content-Security-Policy: base-uri <source>; Content-Security-Policy: base-uri <source> <source>;
While this directive uses the same arguments as other CSP directives, some of them don’t make sense for `<base>`, such as the keywords
<source> can be one of the following:
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
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
'unsafe-inline'are ignored. See script-src for an example.
Requires a sample of the violating code to be included in the violation report.
<meta http-equiv="Content-Security-Policy" content="base-uri 'self'">
<IfModule mod_headers.c> Header set Content-Security-Policy "base-uri 'self'"; </IfModule>
add_header Content-Security-Policy "base-uri 'self';"
Since your domain isn't
<base> element with its
href set to
https://example.com will result in a CSP violation.
<meta http-equiv="Content-Security-Policy" content="base-uri 'self'"> <base href="https://example.com/"> // Error: Refused to set the document's base URI to 'https://example.com/' // because it violates the following Content Security Policy // directive: "base-uri 'self'"
|Content Security Policy Level 3 (Content Security Policy 3)|
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