Vulnerability findings for the public-facing infrastructure of web.telegram.org

Ensure that your web server, application server, load balancer, etc. is configured to set the Content-Security-Policy header.

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Guides/CSP
• https://cheatsheetseries.owasp.org/cheatsheets/Content_Security_Policy_Cheat_Sheet.html
• https://www.w3.org/TR/CSP/
• https://w3c.github.io/webappsec-csp/
• https://web.dev/articles/csp
• https://caniuse.com/#feat=contentsecuritypolicy
• https://content-security-policy.com/

Ensure that the application/web server sets the Cross-Origin-Embedder-Policy header appropriately, and that it sets the Cross-Origin-Embedder-Policy header to 'require-corp' for documents.

If possible, ensure that the end user uses a standards-compliant and modern web browser that supports the Cross-Origin-Embedder-Policy header (https://caniuse.com/mdn-http_headers_cross-origin-embedder-policy).

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cross-Origin-Embedder-Policy

Ensure that the application/web server sets the Cross-Origin-Opener-Policy header appropriately, and that it sets the Cross-Origin-Opener-Policy header to 'same-origin' for documents.

'same-origin-allow-popups' is considered as less secured and should be avoided.

If possible, ensure that the end user uses a standards-compliant and modern web browser that supports the Cross-Origin-Opener-Policy header (https://caniuse.com/mdn-http_headers_cross-origin-opener-policy).

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cross-Origin-Opener-Policy

Ensure that the application/web server sets the Cross-Origin-Resource-Policy header appropriately, and that it sets the Cross-Origin-Resource-Policy header to 'same-origin' for all web pages.

'same-site' is considered as less secured and should be avoided.

If resources must be shared, set the header to 'cross-origin'.

If possible, ensure that the end user uses a standards-compliant and modern web browser that supports the Cross-Origin-Resource-Policy header (https://caniuse.com/mdn-http_headers_cross-origin-resource-policy).

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cross-Origin-Embedder-Policy

See the references for security advice on the use of these functions.

• https://v17.angular.io/guide/security

Ensure that your web server, application server, load balancer, etc. is configured to set the Permissions-Policy header.

• https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Permissions-Policy
• https://developer.chrome.com/blog/feature-policy/
• https://scotthelme.co.uk/a-new-security-header-feature-policy/
• https://w3c.github.io/webappsec-feature-policy/
• https://www.smashingmagazine.com/2018/12/feature-policy/

Ensure that your web server, application server, load balancer, etc. is configured to suppress the "Server" header or provide generic details.

• https://httpd.apache.org/docs/current/mod/core.html#servertokens
• https://learn.microsoft.com/en-us/previous-versions/msp-n-p/ff648552(v=pandp.10)
• https://www.troyhunt.com/shhh-dont-let-your-response-headers/

Ensure that your web server, application server, load balancer, etc. is configured to enforce Strict-Transport-Security.

• https://cheatsheetseries.owasp.org/cheatsheets/HTTP_Strict_Transport_Security_Cheat_Sheet.html
• https://owasp.org/www-community/Security_Headers
• https://en.wikipedia.org/wiki/HTTP_Strict_Transport_Security
• https://caniuse.com/stricttransportsecurity
• https://datatracker.ietf.org/doc/html/rfc6797

Manually confirm that the timestamp data is not sensitive, and that the data cannot be aggregated to disclose exploitable patterns.

• https://cwe.mitre.org/data/definitions/200.html

Ensure that the application/web server sets the Content-Type header appropriately, and that it sets the X-Content-Type-Options header to 'nosniff' for all web pages.

If possible, ensure that the end user uses a standards-compliant and modern web browser that does not perform MIME-sniffing at all, or that can be directed by the web application/web server to not perform MIME-sniffing.

• https://learn.microsoft.com/en-us/previous-versions/windows/internet-explorer/ie-developer/compatibility/gg622941(v=vs.85)
• https://owasp.org/www-community/Security_Headers

This is an informational alert and so no changes are required.

The content may be marked as storable by ensuring that the following conditions are satisfied:

The request method must be understood by the cache and defined as being cacheable ("GET", "HEAD", and "POST" are currently defined as cacheable)

The response status code must be understood by the cache (one of the 1XX, 2XX, 3XX, 4XX, or 5XX response classes are generally understood)

The "no-store" cache directive must not appear in the request or response header fields

For caching by "shared" caches such as "proxy" caches, the "private" response directive must not appear in the response

For caching by "shared" caches such as "proxy" caches, the "Authorization" header field must not appear in the request, unless the response explicitly allows it (using one of the "must-revalidate", "public", or "s-maxage" Cache-Control response directives)

In addition to the conditions above, at least one of the following conditions must also be satisfied by the response:

It must contain an "Expires" header field

It must contain a "max-age" response directive

For "shared" caches such as "proxy" caches, it must contain a "s-maxage" response directive

It must contain a "Cache Control Extension" that allows it to be cached

It must have a status code that is defined as cacheable by default (200, 203, 204, 206, 300, 301, 404, 405, 410, 414, 501).

• https://datatracker.ietf.org/doc/html/rfc7234
• https://datatracker.ietf.org/doc/html/rfc7231
• https://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html

For secure content, ensure the cache-control HTTP header is set with "no-cache, no-store, must-revalidate". If an asset should be cached consider setting the directives "public, max-age, immutable".

• https://cheatsheetseries.owasp.org/cheatsheets/Session_Management_Cheat_Sheet.html#web-content-caching
• https://developer.mozilla.org/en-US/docs/Web/HTTP/Reference/Headers/Cache-Control
• https://grayduck.mn/2021/09/13/cache-control-recommendations/

Validate that the response does not contain sensitive, personal or user-specific information. If it does, consider the use of the following HTTP response headers, to limit, or prevent the content being stored and retrieved from the cache by another user:

Cache-Control: no-cache, no-store, must-revalidate, private

Pragma: no-cache

Expires: 0

This configuration directs both HTTP 1.0 and HTTP 1.1 compliant caching servers to not store the response, and to not retrieve the response (without validation) from the cache, in response to a similar request.

• https://datatracker.ietf.org/doc/html/rfc7234
• https://datatracker.ietf.org/doc/html/rfc7231
• https://www.w3.org/Protocols/rfc2616/rfc2616-sec13.html