Telegram Desktop before 7.2.9 contains an IPC record-separator injection vulnerability in Core::Sandbox that allows remote attackers to inject OPEN: records via crafted tg:// links containing unescaped semicolons. Attackers can reach the interpret: scheme handler to upload local files, including tdata session keys, to an attacker channel, enabling account takeover.

Telegram Desktop before 6.9.4 allows XSS in the HTML exporter. (The first fixed stable version is 7.0.1.) This occurs in button.text.toUtf8 in exportoutputhtml.cpp. Exploitation cannot occur unless HTML export was used by a victim. However, the exploit payload can be exported if a message were forwarded into a group by a member (it is not necessary for the message author to be a member of a group).

A security vulnerability has been detected in Telegram Desktop up to 6.7.5. This vulnerability affects the function RequestButton of the file Telegram/SourceFiles/boxes/urlauthbox.cpp of the component Bot API. The manipulation of the argument loginurl leads to null pointer dereference. It is possible to initiate the attack remotely. The exploit has been disclosed publicly and may be used. There is ongoing doubt regarding the real existence of this vulnerability. Upgrading to version 6.7.6 is able to resolve this issue. Upgrading the affected component is recommended. The vendor provides this rationale for the dispute: "[T]he described scenario does not lead to any security issue or vulnerability, and only causes a one-time crash. In the outlined scenario, the targeted user must perform an active action, which doesn't produce any consequences after the app is relaunched."

Telegram Desktop 2.9.2 contains a denial of service vulnerability that allows attackers to crash the application by sending an oversized message payload. Attackers can generate a 9 million byte buffer and paste it into the messaging interface to trigger an application crash.