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Fix Teams tab SSO broken by SameSite=Lax session cookies #3247

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Fix Teams tab SSO broken by SameSite=Lax session cookies #3247

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274e889
Fix Teams tab SSO broken by SameSite=Lax session cookies
patmr7 Jul 3, 2026
22f32c4
Fix Teams tab SSO broken by SameSite=Lax session cookies
patmr7 Jul 6, 2026
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20 changes: 20 additions & 0 deletions local/o365/sso_login.php
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Original file line number Diff line number Diff line change
Expand Up @@ -169,6 +169,26 @@
}

if ($loginsuccess) {
// Force theme.
$customtheme = get_config('local_o365', 'customtheme');
if (!empty($customtheme) && get_config('theme_' . $customtheme, 'version')) {
$SESSION->theme = $customtheme;
} else if (get_config('theme_boost_o365teams', 'version')) {
$SESSION->theme = 'boost_o365teams';
}

// The session cookie set by core carries SameSite=Lax (MDL-83526), which browsers reject in
// the cross-site iframe of the Teams tab, so re-emit it with "SameSite=None; Secure".
if (is_https() || !empty($CFG->sslproxy)) {
$cookieparams = session_get_cookie_params();
setcookie(session_name(), session_id(), [
'path' => $cookieparams['path'],
'domain' => $cookieparams['domain'],
'secure' => true,
'httponly' => $cookieparams['httponly'],
'samesite' => 'None',
]);
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Comment on lines +183 to +190
}
http_response_code(200);
} else {
http_response_code(401);
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