HTTP security headers: An easy way to harden your web applications | Disk Tech

What are HTTP safety headers?

HTTP safety headers are a subset of HTTP headers that’s associated particularly to safety. They’re exchanged between a shopper (normally an internet browser) and a server to specify the safety particulars of HTTP communication. There are additionally different HTTP headers that, though circuitously associated to privateness and safety, can be thought-about HTTP safety headers.

Setting appropriate headers in your net purposes and net server settings is a simple approach to vastly enhance the resilience of your net software in opposition to many widespread assaults, together with cross-site scripting (XSS) and clickjacking assaults. This put up solely lists a very powerful headers – see our white paper on HTTP safety headers for a extra detailed dialogue of accessible safety headers.

How HTTP safety headers can enhance net software safety

Once we discuss net software safety on this weblog, we regularly imply discovering exploitable vulnerabilities and fixing them in software code. HTTP safety headers function on a unique degree, offering an additional layer of safety by limiting behaviors permitted by the browser and server as soon as the net software is operating. Implementing the appropriate headers in the appropriate means is a vital facet of any best-practice software setup – however how do you select those that make the largest distinction?

As with different net applied sciences, HTTP protocol headers come and go relying on present protocol specs and assist from browser distributors. Particularly in safety, the place de facto requirements can come up and fall out of favor fairly independently of official specs, it’s commonplace to seek out headers that had been broadly supported a number of years in the past however are deprecated at this time. On the similar time, fully new proposals can acquire common assist in a matter of months. Maintaining with the most recent developments isn’t simple, however main software safety options reminiscent of Invicti may also help by robotically checking for the presence and correctness of HTTP safety headers and offering clear suggestions.

An important HTTP safety headers

First up are the three best-known and doubtless most necessary HTTP response headers that any trendy net software must be setting to right away rule out complete lessons of net assaults.


When enabled on the server, the HTTP Strict Transport Safety header (HSTS) enforces the usage of encrypted HTTPS connections as a substitute of plain-text HTTP communication. A typical HSTS header may appear to be this:

Strict-Transport-Safety: max-age=63072000; includeSubDomains; preload

This informs any visiting net browser that the location and all its subdomains use solely SSL/TLS communication, and that the browser ought to default to accessing it over HTTPS for the following two years (the max-age worth in seconds). The preload directive signifies that the location is current on a worldwide record of HTTPS-only websites. The aim of preloading is to hurry up web page hundreds and remove the chance of man-in-the-middle (MITM) assaults when a web site is visited for the primary time.

Invicti checks if HSTS is enabled and appropriately configured.

Content material-Safety-Coverage

The Content material Safety Coverage header (CSP) is one thing of a Swiss Military knife amongst HTTP safety headers. It permits you to exactly management permitted content material sources and plenty of different content material parameters and is advisable approach to defend your web sites and purposes in opposition to XSS assaults. A fundamental CSP header to permit solely belongings from the native origin is:

Content material-Safety-Coverage: default-src 'self'

Different directives embrace script-src, style-src, and img-src to specify permitted sources for scripts, CSS stylesheets, and pictures. For instance, if you happen to specify script-src 'self', you’re limiting scripts (however not different content material) to the native origin. Amongst different issues, you may as well limit browser plugin sources utilizing plugin-types (unsupported in Firefox) or object-src.

Invicti checks if the CSP header is current.


This header was launched means again in 2008 in Microsoft Web Explorer to supply safety in opposition to cross-site scripting assaults involving HTML iframes. To fully stop the present web page from being loaded into iframes, you possibly can specify:

X-Body-Choices: deny

Different supported values are sameorigin to solely permit loading into iframes with the identical origin and allow-from to point particular permitted URLs. Notice that these days, this header can normally get replaced by appropriate CSP directives.

Invicti checks if the X-Body-Choices header is current.

Examples of deprecated HTTP safety headers

As already talked about, some headers get launched as short-term fixes for particular safety points. As net expertise strikes on or requirements catch up, these change into deprecated, usually after just a few years. Listed here are two examples of deprecated headers that had been meant to deal with particular vulnerabilities.


Because the identify suggests, the X-XSS-Safety header was launched to guard in opposition to JavaScript injection assaults within the type of cross-site scripting. The same old syntax was:

X-XSS-Safety: 1; mode=block

Created for browsers geared up with XSS filters, this non-standard header was meant as a approach to management the filtering performance. In follow, it was comparatively simple to bypass or abuse. Since trendy browsers now not use XSS filtering, this header is now deprecated.

Invicti checks when you’ve got set X-XSS-Safety in your web sites.


HTTP Public Key Pinning (HPKP) was launched in Google Chrome and Firefox to resolve the issue of certificates spoofing. HPKP was a sophisticated mechanism that concerned the server presenting shoppers with cryptographic hashes of legitimate certificates public keys for future communication. A typical header could be one thing like:


In follow, public key pinning proved too sophisticated to make use of. If configured incorrectly, the header might fully disable web site entry for the time specified within the max‑age parameter (within the instance above, this might be two months). The header was deprecated in favor of certificates transparency logs – see the Anticipate-CT header beneath.

Different helpful HTTP safety headers

Whereas not as crucial to implement as CSP and HSTS, the extra headers beneath may also make it easier to harden your net purposes with comparatively little effort.


The advisable approach to stop web site certificates spoofing is to make use of the Anticipate-CT header to point that solely new certificates added to Certificates Transparency logs must be accepted. A typical header could be:

Anticipate-CT: max-age=86400, implement, 

The implement directive instructs shoppers to refuse connections that violate the Certificates Transparency coverage. The non-obligatory report-uri directive signifies a location for reporting connection failures.

Invicti stories lacking Anticipate-CT headers with a Greatest Follow severity degree.

X-Content material-Kind-Choices

When included in server responses, this header forces net browsers to strictly observe the MIME sorts laid out in Content material-Kind headers. That is particularly meant to guard web sites from cross-site scripting assaults that abuse MIME sniffing to provide malicious code masquerading as a non-executable MIME sort. The header has only one directive:

X-Content material-Kind-Choices: nosniff

Invicti checks if Content material-Kind headers are set and X-Content material-Kind-Choices: nosniff is current.

Fetch metadata headers

This comparatively new set of client-side headers permits the browser to tell the server about application-specific HTTP request attributes. 4 headers at present exist:

  • Sec-Fetch-Web site: Specifies the meant relationship between the initiator and goal origin
  • Sec-Fetch-Mode: Specifies the meant request mode
  • Sec-Fetch-Consumer: Specifies if the request was triggered by the person
  • Sec-Fetch-Dest: Specifies the meant request vacation spot

When supported by each the server and the browser, these headers present the server with further details about meant software behaviors to assist determine and block suspicious requests.

Associated HTTP headers to enhance privateness and safety

These remaining objects usually are not strictly HTTP safety headers however can serve to enhance each safety and privateness.


This controls how a lot (if any) referrer info the browser ought to divulge to the net server. Typical utilization could be:

Referrer-Coverage: origin-when-cross-origin

With this header worth, the browser will solely reveal its full referrer info (together with the URL) for same-origin requests. For all different requests, solely details about the origin is shipped.

Invicti stories lacking Referrer-Coverage headers with a Greatest Follow severity degree.


This header means that you can management the caching of particular net pages. A number of directives can be found, however the typical utilization is solely:

Cache-Management: no-store

This prevents any caching of the server response, which could be helpful for guaranteeing that confidential information isn’t retained in any caches. You should utilize different out there directives to get extra exact management over caching habits.

Clear-Web site-Information

If you wish to be sure that confidential info out of your software isn’t saved by the browser after a person logs out, you possibly can set the Clear-Web site-Information header:

Clear-Web site-Information: "*"

This directive will clear all looking information associated to the location. The cache, cookies, and storage directives are additionally out there to offer you extra fine-grained management over what’s cleared.


That is an experimental header that means that you can deny entry to particular browser options and APIs on the present web page. It may be used to regulate software performance but in addition to enhance privateness and safety. For instance, if you wish to deny an software permission to entry the microphone and digicam APIs, you possibly can ship the next header:

Characteristic-Coverage: microphone 'none'; digicam 'none'

Many extra directives can be found – see the Characteristic-Coverage documentation on MDN for a full record.

Safety headers in motion with Sven Morgenroth

Invicti safety researcher Sven Morgenroth joined Paul Asadoorian on Paul’s Safety Weekly #652 to explain and display numerous HTTP headers associated to safety. Watch the total video interview and demo:

Maintain observe of your HTTP safety headers with Invicti

HTTP safety headers could be a simple means to enhance net safety and sometimes don’t require modifications to the applying itself, so it’s at all times a good suggestion to make use of probably the most present headers. Nonetheless, as a result of browser vendor assist for HTTP headers can change so shortly, it’s arduous to maintain the whole lot up-to-date, particularly if you happen to’re working with tons of of internet sites. 

That will help you sustain and keep safe, Invicti supplies vulnerability checks that embrace testing for advisable HTTP safety headers. Invicti checks if a header is current and appropriately configured, and supplies clear suggestions to make sure that your net purposes at all times have the most effective safety.

HTTP security headers: An easy way to harden your web applications