DiscordNotifications is an extension for MediaWiki that sends notifications of actions in your Wiki to a Discord channel. DiscordNotifications allows sending requests via curl and file_get_contents to arbitrary URLs set via $wgDiscordIncomingWebhookUrl and $wgDiscordAdditionalIncomingWebhookUrls. This allows for DOS by causing the server to read large files. SSRF is also possible if there are internal unprotected APIs that can be accessed using HTTP POST requests, which could also possibly lead to RCE. This vulnerability is fixed in commit 1f20d850cbcce5b15951c7c6127b87b927a5415e.
The product does not properly control the allocation and maintenance of a limited resource.
Mitigation of resource exhaustion attacks requires that the target system either:
The first of these solutions is an issue in itself though, since it may allow attackers to prevent the use of the system by a particular valid user. If the attacker impersonates the valid user, they may be able to prevent the user from accessing the server in question.
The second solution is simply difficult to effectively institute – and even when properly done, it does not provide a full solution. It simply makes the attack require more resources on the part of the attacker.