Use AllowedMentions to disable mentions everywhere by default

PluralKit.Bot/Bot.cs

@@ -155,7 +155,7 @@ namespace PluralKit.Bot
                 if (reportChannel != null && reportChannel.BotHasAllPermissions(Permissions.SendMessages))
                 {
                     var eid = sentryEvent.EventId;
-                    await reportChannel.SendMessageAsync(
+                    await reportChannel.SendMessageFixedAsync(
                         $"{Emojis.Error} Internal error occurred. Please join the support server (<https://discord.gg/PczBt78>), and send the developer this ID: `{eid}`\nBe sure to include a description of what you were doing to make the error occur.");
                 }
             }

PluralKit.Bot/CommandSystem/Context.cs

@@ -1,4 +1,5 @@
 using System;
+using System.Collections.Generic;
 using System.Linq;
 using System.Threading.Tasks;
 
@@ -66,7 +67,7 @@ namespace PluralKit.Bot
         public bool HasNext(bool skipFlags = true) => RemainderOrNull(skipFlags) != null;
         public string FullCommand => _parameters.FullCommand;
 
-        public Task<DiscordMessage> Reply(string text = null, DiscordEmbed embed = null)
+        public Task<DiscordMessage> Reply(string text = null, DiscordEmbed embed = null, IEnumerable<IMention> mentions = null)
         {
             if (!this.BotHasAllPermissions(Permissions.SendMessages))
                 // Will be "swallowed" during the error handler anyway, this message is never shown.
@@ -74,8 +75,7 @@ namespace PluralKit.Bot
 
             if (embed != null && !this.BotHasAllPermissions(Permissions.EmbedLinks))
                 throw new PKError("PluralKit does not have permission to send embeds in this channel. Please ensure I have the **Embed Links** permission enabled.");
-            
+            return Channel.SendMessageFixedAsync(text, embed: embed, mentions: mentions);
-            return Channel.SendMessageAsync(text, embed: embed);
         }
 
         /// <summary>

PluralKit.Bot/Commands/SystemLink.cs

@@ -1,6 +1,8 @@
 using System.Linq;
 using System.Threading.Tasks;
 
+using DSharpPlus.Entities;
+
 using PluralKit.Core;
 
 namespace PluralKit.Bot
@@ -25,7 +27,8 @@ namespace PluralKit.Bot
             var existingAccount = await _data.GetSystemByAccount(account.Id);
             if (existingAccount != null) throw Errors.AccountInOtherSystem(existingAccount); 
 
-            var msg = await ctx.Reply($"{account.Mention}, please confirm the link by clicking the {Emojis.Success} reaction on this message.");
+            var msg = await ctx.Reply($"{account.Mention}, please confirm the link by clicking the {Emojis.Success} reaction on this message.",
+                mentions: new IMention[] { new UserMention(account) });
             if (!await ctx.PromptYesNo(msg, user: account)) throw Errors.MemberLinkCancelled;
             await _data.AddAccount(ctx.System, account.Id);
             await ctx.Reply($"{Emojis.Success} Account linked to system.");

PluralKit.Bot/Commands/Token.cs

@@ -29,8 +29,8 @@ namespace PluralKit.Bot
 
             // DM the user a security disclaimer, and then the token in a separate message (for easy copying on mobile)
             var dm = await ctx.Rest.CreateDmAsync(ctx.Author.Id);
-            await dm.SendMessageAsync($"{Emojis.Warn} Please note that this grants access to modify (and delete!) all your system data, so keep it safe and secure. If it leaks or you need a new one, you can invalidate this one with `pk;token refresh`.\n\nYour token is below:");
+            await dm.SendMessageFixedAsync($"{Emojis.Warn} Please note that this grants access to modify (and delete!) all your system data, so keep it safe and secure. If it leaks or you need a new one, you can invalidate this one with `pk;token refresh`.\n\nYour token is below:");
-            await dm.SendMessageAsync(token);
+            await dm.SendMessageFixedAsync(token);
         }
 
         private async Task<string> MakeAndSetNewToken(PKSystem system)
@@ -63,8 +63,8 @@ namespace PluralKit.Bot
 
             // DM the user an invalidation disclaimer, and then the token in a separate message (for easy copying on mobile)
             var dm = await ctx.Rest.CreateDmAsync(ctx.Author.Id);
-            await dm.SendMessageAsync($"{Emojis.Warn} Your previous API token has been invalidated. You will need to change it anywhere it's currently used.\n\nYour token is below:");
+            await dm.SendMessageFixedAsync($"{Emojis.Warn} Your previous API token has been invalidated. You will need to change it anywhere it's currently used.\n\nYour token is below:");
-            await dm.SendMessageAsync(token);
+            await dm.SendMessageFixedAsync(token);
         }
     }
 }

PluralKit.Bot/Handlers/MessageCreated.cs

@@ -122,7 +122,7 @@ namespace PluralKit.Bot
                 // User-facing errors, print to the channel properly formatted
                 var msg = evt.Message;
                 if (msg.Channel.Guild == null || msg.Channel.BotHasAllPermissions(Permissions.SendMessages))
-                    await msg.Channel.SendMessageAsync($"{Emojis.Error} {e.Message}");
+                    await msg.Channel.SendMessageFixedAsync($"{Emojis.Error} {e.Message}");
             }
 
             return false;

PluralKit.Bot/Handlers/ReactionAdded.cs

@@ -108,15 +108,16 @@ namespace PluralKit.Bot
             {
                 // If the system has pings enabled, go ahead
                 var embed = new DiscordEmbedBuilder().WithDescription($"[Jump to pinged message]({evt.Message.JumpLink})");
-                await evt.Channel.SendMessageAsync($"Psst, **{msg.Member.DisplayName()}** (<@{msg.Message.Sender}>), you have been pinged by <@{evt.User.Id}>.", embed: embed.Build());
+                await evt.Channel.SendMessageFixedAsync($"Psst, **{msg.Member.DisplayName()}** (<@{msg.Message.Sender}>), you have been pinged by <@{evt.User.Id}>.", embed: embed.Build(),
+                    new IMention[] {new UserMention(msg.Message.Sender) });
             }
             else
             {
                 // If not, tell them in DMs (if we can)
                 try
                 {
-                    await guildUser.SendMessageAsync($"{Emojis.Error} {msg.Member.DisplayName()}'s system has disabled reaction pings. If you want to mention them anyway, you can copy/paste the following message:");
+                    await guildUser.SendMessageFixedAsync($"{Emojis.Error} {msg.Member.DisplayName()}'s system has disabled reaction pings. If you want to mention them anyway, you can copy/paste the following message:");
-                    await guildUser.SendMessageAsync($"`<@{msg.Message.Sender}>`");
+                    await guildUser.SendMessageFixedAsync($"`<@{msg.Message.Sender}>`");
                 }
                 catch (UnauthorizedException) { }
             }

PluralKit.Bot/Proxy/ProxyService.cs

@@ -130,14 +130,14 @@ namespace PluralKit.Bot
             if ((permissions & Permissions.ManageWebhooks) == 0)
             {
                 // todo: PKError-ify these
-                await channel.SendMessageAsync(
+                await channel.SendMessageFixedAsync(
                     $"{Emojis.Error} PluralKit does not have the *Manage Webhooks* permission in this channel, and thus cannot proxy messages. Please contact a server administrator to remedy this.");
                 return false;
             }
 
             if ((permissions & Permissions.ManageMessages) == 0)
             {
-                await channel.SendMessageAsync(
+                await channel.SendMessageFixedAsync(
                     $"{Emojis.Error} PluralKit does not have the *Manage Messages* permission in this channel, and thus cannot delete the original trigger message. Please contact a server administrator to remedy this.");
                 return false;
             }

PluralKit.Bot/Services/LogChannelService.cs

@@ -44,7 +44,7 @@ namespace PluralKit.Bot {
                 await conn.QueryMember(proxy.Member.Id), hookMessage, trigger.Id, trigger.Author, proxy.Content,
                 trigger.Channel);
             var url = $"https://discord.com/channels/{trigger.Channel.GuildId}/{trigger.ChannelId}/{hookMessage}";
-            await logChannel.SendMessageAsync(content: url, embed: embed);
+            await logChannel.SendMessageFixedAsync(content: url, embed: embed);
         }
 
         private async Task<DiscordChannel> FindLogChannel(ulong guild, ulong channel)

PluralKit.Bot/Utils/DiscordUtils.cs

@@ -105,5 +105,17 @@ namespace PluralKit.Bot
             // Workaround for https://github.com/DSharpPlus/DSharpPlus/issues/565
             return input?.Replace("%20", "+");
         }
+        
+        // Passing an empty list (counter-intuitively) *allows* all mentions through (even if non-null)
+        // So we add a single "bogus" user mention for ID=1 that'll never actually resolve, and thus block all (other) mentions
+        private static readonly IEnumerable<IMention> DenyAllMentions = new IMention[] {new UserMention(1)}; 
+
+        public static Task<DiscordMessage> SendMessageFixedAsync(this DiscordChannel channel, string content = null, DiscordEmbed embed = null, IEnumerable<IMention> mentions = null) =>
+            channel.SendMessageAsync(content, embed: embed, mentions: mentions ?? DenyAllMentions);
+        
+        // This doesn't do anything by itself (DiscordMember.SendMessageAsync doesn't take a mentions argument)
+        // It's just here for consistency so we don't use the standard SendMessageAsync method >.>
+        public static Task<DiscordMessage> SendMessageFixedAsync(this DiscordMember member, string content = null, DiscordEmbed embed = null) =>
+            member.SendMessageAsync(content, embed: embed);
     }
 }