"Turn off link previews in everything, especially mail apps and anything related to notifications.
Sick.Codes said the rendering method is still functional in all of the tested apps, and suggests users of all IM apps is the following: NIST is currently investigating the scope and the impact of the vulnerabilities, so if they had been fixed in past versions, it will be determined by the organization soon.Īs such, users of the mentioned apps should be cautious when receiving messages containing URLs, always click on the left side, and remain on alert for incoming app security updates that may address the issue. Sick.Codes told BleepingComputer that the messaging apps listed above are still vulnerable to this rendering method. Telegram used to be vulnerable too, but it was the first to address the problem via a security update.Īlso, Signal's development team has responded to Sick.Codes' report immediately and told the researcher a fix is coming in the next release of the app. The same attack is likely applicable to many more IM and email apps, but only those mentioned above have been confirmed as vulnerable. In fact, there's abundant evidence of RTLO-based exploitation in the wild, even when it involves more complex technical concepts. The one-liner PoC is publicly available and straightforward to use even by people with poor technical understanding or no hacking skills. While the URL is displayed as a single string with the reverse text, the RTLO Unicode character in the hyperlink is converted to its hexadecimal equivalent, leaving an URL like: Impact and fixes Other tests conducted by BleepingComputer show that this rendering flaw does not work as expected in Gmail,, or ProtonMail. IMessage message preview list show reversed text This means that if a user clicks on the left side of the URL, they will go to, and if they click on the right side, they will go to .Įven stranger, while iMessage on iOS 15 shows the text in reverse in message list preview screen, it removes the reverse string in the actual message. For example, while the combined URLs may appear as a single URL, they are actually treated as two URLs. However, BleepingComputer noticed some peculiarities when testing this bug in iMessage, Signal, and even Gmail. In reality, these destinations could host anything, so the spoofing is highly elusive and tricky to spot.
#IMESSAGE FOR ANDROID 2015 APK#
The resulting URL shown as merged to the recipient (Sick.Codes)Īfter the injected RTLO control character, the URL gets reversed due to treating it as a "right-to-left" language (Arabic, Hebrew, etc.), so the threat actor has to consider when registering the destination domain.įor example, using a crafted 'gepj.xyz' URL would appear as the innocuous JPEG image file 'zyx.jpeg', while crafting "kpa.li" would appear as an APK file 'li.apk', etc. The exploit is a one-liner abusing iOS and Android's trust of gTLDs and support for displaying bi-directional text and is as simple as adding a single control character '\u202E' between two valid URLs.įor example, the released PoC abuses for the masqueraded and clickable URL and sets bit.ly/3ixIRwm as the destination. The two security researchers agreed on the immediate release of the PoC on GitHub since the vulnerabilities may have been under active exploitation for a long time now.
The researcher was reluctant to share more information about the method of exploiting the flaws, which had been demonstrated only on video, so Sick.Codes decided to replicate the exploit on his own and write a proof of concept (PoC) for it. Sick.Codes reached out to the researcher to ask if he had just made his repository public or not, and the researcher responded with surprise about the CVEs being released now, after all that time. The CVE IDs are so old because the initial discovery of the vulnerabilities took place in August 2019 by a researcher named 'zadewg.'įreelance security researcher Sick.Codes noticed the flaws when the CVE Program recently published them on Twitter and decided to investigate further. Signal doesn't have a corresponding CVE ID because the particular attack method was disclosed to them just recently.
The vulnerabilities have been assigned the following CVEs and are known to work in the following versions of IM apps:ĬVE-2020-20093 – Facebook Messenger 227.0 or prior for iOS and 228.1.0.10.116 or prior on AndroidĬVE-2020-20094 – Instagram 106.0 or prior for iOS and 107.0.0.11 or prior on AndroidĬVE-2020-20095 – iMessage 14.3 or older for iOSĬVE-2020-20096 – WhatsApp 2.19.80 or prior for iOS and 2.19.222 or prior on Android Snap from the exploit demo video (GitHub)
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