The Signal app before 5.34 for iOS allows URI spoofing via RTLO injection. It incorrectly renders RTLO encoded URLs beginning with a non-breaking space, when there is a hash character in the URL. This technique allows a remote unauthenticated attacker to send legitimate looking links, appearing to be any website URL, by abusing the non-http/non-https automatic rendering of URLs. An attacker can spoof, for example, example.com, and masquerade any URL with a malicious destination. An attacker requires a subdomain such as gepj, txt, fdp, or xcod, which would appear backwards as jpeg, txt, pdf, and docx respectively.

References

• https://nvd.nist.gov/vuln/detail/CVE-2022-28345
• https://github.com/sickcodes/security/blob/master/advisories/SICK-2022-42.md
• https://github.com/zadewg/RIUS
• https://sick.codes/sick-2022-42
• https://blog.malwarebytes.com/social-engineering/2022/03/uri-spoofing-flaw-could-phish-whatsapp-signal-instagram-and-imessage-users/