It's fortigate SSL VPN.
The full report about this issue:
QID:11827Severity:2
CVSS Base:4.3 AV:N/AC:M/Au:N/C:N/I:P/A:NCVSS Temporal:3.5 E:U/RL:U/RC:URPCI Compliance Status:FAIL 
This QID reports the absence of the following [link=https://www.owasp.org/index.php/OWASP_Secure_Headers_Project#tab=Headers]HTTP headers[/link] according to [link=https://cwe.mitre.org/data/definitions/693.html]CWE-693: Protection Mechanism Failure[/link]: X-Frame-Options: This HTTP response header improves the protection of web applications against clickjacking attacks. Clickjacking, also known as a "UI redress attack", allows an attacker to use multiple transparent or opaque layers to trick a targeted user into clicking on a button or link on another page when they were intending to click on the the top level page. X-XSS-Protection: This HTTP header enables the browser built-in Cross-Site Scripting (XSS) filter to prevent cross-site scripting attacks. X-XSS-Protection: 0; disables this functionality. X-Content-Type-Options: This HTTP header prevents attacks based on MIME-type mismatch. The only possible value is nosniff. If your server returns X-Content-Type-Options: nosniff in the response, the browser will refuse to load the styles and scripts in case they have an incorrect MIME-type. Content-Security-Policy: This HTTP header helps to detect and mitigate certain types of attacks, including Cross Site Scripting (XSS), packet sniffing attacks and data injection attacks. Public-Key-Pins: The Public Key Pinning Extension for HTTP (HPKP) is a security feature that tells a web client to associate a specific cryptographic public key with a certain web server to decrease the risk of MITM attacks with forged certificates. Strict-Transport-Security: The HTTP Strict-Transport-Security response header (HSTS) is a security feature that lets a web site tell browsers that it should only be communicated with using HTTPS, instead of using HTTP.
QID Detection Logic: This unauthenticated QID looks for the presence of the following HTTP responses: Valid directives for X-Frame-Options are: X-Frame-Options: DENY - The page cannot be displayed in a frame, regardless of the site attempting to do so. X-Frame-Options: SAMEORIGIN - The page can only be displayed in a frame on the same origin as the page itself. X-Frame-Options: ALLOW-FROM RESOURCE-URL - The page can only be displayed in a frame on the specified origin.
Content-Security-Policy: frame-ancestors - This directive specifies valid parents that may embed a page using frame, iframe, object, embed, or appletValid directives for X-XSS-Protections are: X-XSS-Protection: 1 - Enables XSS filtering (usually default in browsers). If a cross-site scripting attack is detected, the browser will sanitize the page (remove the unsafe parts). X-XSS-Protection: 1; mode=block - Enables XSS filtering. Rather than sanitizing the page, the browser will prevent rendering of the page if an attack is detected. X-XSS-Protection: 1; report=URI - Enables XSS filtering. If a cross-site scripting attack is detected, the browser will sanitize the page and report the violation. This uses the functionality of the CSP report-uri directive to send a report. X-XSS-Protection: 0 disables this directive and hence is also treated as not detected.
A valid directive for X-Content-Type-Options: nosniff
A valid directive for Content-Security-Policy: <policy-directive>; <policy-directive>
A valid HPKP directive Public-Key-Pins: pin-sha256="base64=="; max-age=expireTime [; includeSubDomains][; report-uri="reportURI"]
A valid HSTS directive Strict-Transport-Security: max-age=<expire-time>; [; includeSubDomains][; preload]
NOTE: All report-only directives (where applicable) are considered invalid.
Impact:Depending on the vulnerability being exploited, an unauthenticated remote attacker could conduct cross-site scripting, clickjacking or MIME-type sniffing attacks.
Solution:CWE-693: Protection Mechanism Failure mentions the following - The product does not use or incorrectly uses a protection mechanism that provides sufficient defense against directed attacks against the product. A "missing" protection mechanism occurs when the application does not define any mechanism against a certain class of attack. An "insufficient" protection mechanism might provide some defenses - for example, against the most common attacks - but it does not protect against everything that is intended. Finally, an "ignored" mechanism occurs when a mechanism is available and in active use within the product, but the developer has not applied it in some code path.
Customers are advised to set proper [link=https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Frame-Options]X-Frame-Options[/link], [link=https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-XSS-Protection]X-XSS-Protection[/link], [link=https://developer.mozilla.org/en-US/docs/Web/HTTP/CSP]Content Security Policy[/link], [link=https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/X-Content-Type-Options]X-Content-Type-Options[/link], [link=https://developer.mozilla.org/en-US/docs/Web/HTTP/Public_Key_Pinning]Public Key Pinning[/link] and [link=https://developer.mozilla.org/en-US/docs/Web/HTTP/Headers/Strict-Transport-Security]Strict-Transport-Security[/link] HTTP response headers.
Depending on their server software, customers can set directives in their site configuration or Web.config files. Few examples are:
X-Frame-Options: Apache: Header always append X-Frame-Options SAMEORIGIN nginx: add_header X-Frame-Options SAMEORIGIN; HAProxy: rspadd X-Frame-Options:\ SAMEORIGIN IIS: <HTTPPROTOCOL><CUSTOMHEADERS><ADD NAME="X-Frame-Options" VALUE="SAMEORIGIN"></ADD></CUSTOMHEADERS></HTTPPROTOCOL>
X-XSS-Protection: Apache: Header always set X-XSS-Protection "1; mode=block" PHP: header("X-XSS-Protection: 1; mode=block");
X-Content-Type-Options: Apache: Header always set X-Content-Type-Options: nosniff
Content-Security-Policy: (Please note that these values may differ from website to website. The values below are for informational purposes only. The scanner simply looks for the presence of the security header.) Apache: Header set Content-Security-Policy "script-src 'self'; object-src 'self'" IIS: <SYSTEM.WEBSERVER><HTTPPROTOCOL><CUSTOMHEADERS><ADD NAME="Content-Security-Policy" VALUE="default-src 'self';"></ADD></CUSTOMHEADERS></HTTPPROTOCOL></SYSTEM.WEBSERVER> nginx: add_header Content-Security-Policy "default-src 'self'; script-src 'self';
HTTP Public Key Pinning (HPKP): Apache: Header always set Public-Key-Pins "pin-sha256="base64+primary=="; pin-sha256="base64+backup=="; max-age=5184000; includeSubDomains" Lighttpd: setenv.add-response-header = ( "Public-Key-Pins" => "pin-sha256="base64+primary=="; pin-sha256="base64+backup=="; max-age=5184000; includeSubDomains")
HTTP Strict-Transport-Security: Apache: Header always set Strict-Transport-Security "max-age=31536000; includeSubDomains" Nginx: add_header Strict-Transport-Security max-age=31536000;
Result:X-XSS-Protection HTTP Header missing on port 443.
GET / HTTP/1.0
Host: x.x.x.x
X-Content-Type-Options HTTP Header missing on port 443.
Content-Security-Policy HTTP Header missing on port 443.
Public-Key-Pins HTTP Header missing on port 443.
Strict-Transport-Security HTTP Header missing on port 443.
