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fix: prevent users from inviting themselves in referral flow #386

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fix: prevent users from inviting themselves in referral flow #386

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21 changes: 17 additions & 4 deletions src/app/api/referrals/route.ts
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Original file line number Diff line number Diff line change
Expand Up @@ -4,6 +4,8 @@ import { referralInviteEmail, sendEmail } from "@/lib/email";
import { createServiceClient } from "@/lib/supabase/service";

type AnySupabase = any;
const MAX_EMAIL_ENTRIES_PER_REQUEST = 200;
const MAX_INVITES_PER_REQUEST = 20;

// GET /api/referrals - List my referrals
export async function GET(request: NextRequest) {
Expand Down Expand Up @@ -69,9 +71,9 @@ export async function POST(request: NextRequest) {
);
}

if (emails.length > 20) {
if (emails.length > MAX_EMAIL_ENTRIES_PER_REQUEST) {
return NextResponse.json(
{ error: "Maximum 20 invites at a time" },
{ error: `Maximum ${MAX_EMAIL_ENTRIES_PER_REQUEST} email entries at a time` },
{ status: 400 }
);
}
Expand All @@ -80,11 +82,22 @@ export async function POST(request: NextRequest) {
// Only valid emails should count toward throttle limits
const emailRegex = /^[^\s@]+@[^\s@]+\.[^\s@]+$/;
const normalizedEmails = emails.map((e: string) => e.trim().toLowerCase());
const validEmails = normalizedEmails.filter((e: string) => emailRegex.test(e));
const userEmail = user.email?.toLowerCase();
const validEmails = Array.from(
new Set(normalizedEmails.filter((e: string) => emailRegex.test(e) && e !== userEmail))
);
Comment on lines +85 to +88

@greptile-apps greptile-apps Bot Jun 4, 2026

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P1 user.email is typed as string | undefined in Supabase Auth — the optional-chain on line 85 confirms the developer knows this. When userEmail resolves to undefined, the filter condition e !== userEmail becomes e !== undefined, which is always true for any email string. That means the entire self-invite guard is silently bypassed for accounts without a stored email (e.g. certain OAuth providers), and the PR's primary goal is not met for those users.

Suggested change
const userEmail = user.email?.toLowerCase();
const validEmails = Array.from(
new Set(normalizedEmails.filter((e: string) => emailRegex.test(e) && e !== userEmail))
);
const userEmail = user.email?.trim().toLowerCase();
if (!userEmail) {
return NextResponse.json(
{ error: "Unable to determine your email address" },
{ status: 400 }
);
}
const validEmails = Array.from(
new Set(normalizedEmails.filter((e: string) => emailRegex.test(e) && e !== userEmail))
);


if (validEmails.length === 0) {
const onlySelf = normalizedEmails.every(e => e === userEmail || !emailRegex.test(e));
return NextResponse.json(
{ error: onlySelf ? "You cannot invite yourself" : "No valid email addresses provided" },
{ status: 400 }
);
}
Comment on lines 90 to +96

@greptile-apps greptile-apps Bot Jun 4, 2026

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P2 The onlySelf heuristic has a false-positive when userEmail is undefined: the condition e === userEmail becomes e === undefined, which is always false for email strings, so onlySelf falls through entirely to !emailRegex.test(e). Any submission consisting purely of syntactically invalid addresses (e.g. ["notanemail"]) then reports "You cannot invite yourself" even though no self-invite was attempted. Tightening the guard to require at least one entry that matches userEmail avoids the mislead.

Suggested change
if (validEmails.length === 0) {
const onlySelf = normalizedEmails.every(e => e === userEmail || !emailRegex.test(e));
return NextResponse.json(
{ error: onlySelf ? "You cannot invite yourself" : "No valid email addresses provided" },
{ status: 400 }
);
}
if (validEmails.length === 0) {
const hasSelfEntry = userEmail !== undefined && normalizedEmails.some(e => e === userEmail);
const onlySelf = hasSelfEntry && normalizedEmails.every(e => e === userEmail || !emailRegex.test(e));
return NextResponse.json(
{ error: onlySelf ? "You cannot invite yourself" : "No valid email addresses provided" },
{ status: 400 }
);
}


if (validEmails.length > MAX_INVITES_PER_REQUEST) {
return NextResponse.json(
{ error: "No valid email addresses provided" },
{ error: `Maximum ${MAX_INVITES_PER_REQUEST} invites at a time` },
{ status: 400 }
);
}
Expand Down