diff --git a/htdocs/public/eventorganization/attendee_new.php b/htdocs/public/eventorganization/attendee_new.php
index b350ece39f4..55303bcb00e 100644
--- a/htdocs/public/eventorganization/attendee_new.php
+++ b/htdocs/public/eventorganization/attendee_new.php
@@ -19,16 +19,6 @@
  *	\file       htdocs/public/eventorganization/attendee_new.php
  *	\ingroup    project
  *	\brief      Example of form to subscribe to an event
- *
- *  Note that you can add following constant to change behaviour of page
- *  MEMBER_NEWFORM_AMOUNT               Default amount for auto-subscribe form
- *  MEMBER_NEWFORM_EDITAMOUNT           0 or 1 = Amount can be edited
- *  MEMBER_NEWFORM_PAYONLINE            Suggest payment with paypal, paybox or stripe
- *  MEMBER_NEWFORM_DOLIBARRTURNOVER     Show field turnover (specific for dolibarr foundation)
- *  MEMBER_URL_REDIRECT_SUBSCRIPTION    Url to redirect once subscribe submitted
- *  MEMBER_NEWFORM_FORCETYPE            Force type of member
- *  MEMBER_NEWFORM_FORCEMORPHY          Force nature of member (mor/phy)
- *  MEMBER_NEWFORM_FORCECOUNTRYCODE     Force country
  */
 
 if (!defined('NOLOGIN')) {
diff --git a/htdocs/public/members/new.php b/htdocs/public/members/new.php
index 6589f2a17d0..055ffec56f9 100644
--- a/htdocs/public/members/new.php
+++ b/htdocs/public/members/new.php
@@ -30,6 +30,7 @@
  *  Note that you can add following constant to change behaviour of page
  *  MEMBER_NEWFORM_AMOUNT               Default amount for auto-subscribe form
  *  MEMBER_NEWFORM_EDITAMOUNT           0 or 1 = Amount can be edited
+ *  MEMBER_MIN_AMOUNT                   Minimum amount
  *  MEMBER_NEWFORM_PAYONLINE            Suggest payment with paypal, paybox or stripe
  *  MEMBER_NEWFORM_DOLIBARRTURNOVER     Show field turnover (specific for dolibarr foundation)
  *  MEMBER_URL_REDIRECT_SUBSCRIPTION    Url to redirect once subscribe submitted
diff --git a/htdocs/public/payment/newpayment.php b/htdocs/public/payment/newpayment.php
index 5158e294fb2..d25e14288f8 100644
--- a/htdocs/public/payment/newpayment.php
+++ b/htdocs/public/payment/newpayment.php
@@ -481,7 +481,7 @@ if ($action == 'dopayment') {
 
 
 // Called when choosing Stripe mode.
-// When using the Charge API architecture, this code is called after clicking the 'dopayment' with the Charge API architecture.
+// When using the old Charge API architecture, this code is called after clicking the 'dopayment' with the Charge API architecture.
 // When using the PaymentIntent API architecture, the Stripe customer was already created when creating PaymentIntent when showing payment page, and the payment is already ok when action=charge.
 if ($action == 'charge' && !empty($conf->stripe->enabled)) {
 	$amountstripe = $amount;
@@ -728,7 +728,7 @@ if ($action == 'charge' && !empty($conf->stripe->enabled)) {
 		}
 	}
 
-	// When using the PaymentIntent API architecture
+	// When using the PaymentIntent API architecture (mode set on by default into conf.class.php)
 	if (!empty($conf->global->STRIPE_USE_INTENT_WITH_AUTOMATIC_CONFIRMATION)) {
 		$service = 'StripeTest';
 		$servicestatus = 0;
@@ -793,8 +793,8 @@ if ($action == 'charge' && !empty($conf->stripe->enabled)) {
 	$remoteip = getUserRemoteIP();
 
 	$_SESSION["onlinetoken"] = $stripeToken;
-	$_SESSION["FinalPaymentAmt"] = $amount;
-	$_SESSION["currencyCodeType"] = $currency;
+	$_SESSION["FinalPaymentAmt"] = $amount;			// amount really paid (coming from Stripe). Will be used for check in paymentok.php.
+	$_SESSION["currencyCodeType"] = $currency;		// currency really used for payment (coming from Stripe). Will be used for check in paymentok.php.
 	$_SESSION["paymentType"] = '';
 	$_SESSION['ipaddress'] = ($remoteip ? $remoteip : 'unknown'); // Payer ip
 	$_SESSION['payerID'] = is_object($customer) ? $customer->id : '';
diff --git a/htdocs/public/payment/paymentok.php b/htdocs/public/payment/paymentok.php
index c822bfcdf96..ea86f28a894 100644
--- a/htdocs/public/payment/paymentok.php
+++ b/htdocs/public/payment/paymentok.php
@@ -417,7 +417,7 @@ if ($ispaymentok) {
 			// Do action only if $FinalPaymentAmt is set (session variable is cleaned after this page to avoid duplicate actions when page is POST a second time)
 			if (!empty($FinalPaymentAmt) && $paymentTypeId > 0) {
 				// Security protection:
-				if (empty($conf->global->MEMBER_NEWFORM_EDITAMOUNT)) {	// If we didn't allow members to choose their membership amount
+				if (empty($conf->global->MEMBER_NEWFORM_EDITAMOUNT)) {	// If we didn't allow members to choose their membership amount (if free amount is allowed, no need to check)
 					if ($object->status == $object::STATUS_DRAFT) {		// If the member is not yet validated, we check that the amount is the same as expected.
 						$typeid = $object->typeid;
 
@@ -440,6 +440,17 @@ if ($ispaymentok) {
 					}
 				}
 
+				// Security protection:
+				if (!empty($conf->global->MEMBER_MIN_AMOUNT)) {
+					if ($FinalPaymentAmt < $conf->global->MEMBER_MIN_AMOUNT) {
+						$error++;
+						$errmsg = 'Value of FinalPayment ('.$FinalPaymentAmt.') is lower than the minimum allowed ('.$conf->global->MEMBER_MIN_AMOUNT.'). May be a hack to try to pay a different amount ?';
+						$postactionmessages[] = $errmsg;
+						$ispostactionok = -1;
+						dol_syslog("Failed to validate member (amount lower than minimum): ".$errmsg, LOG_ERR, 0, '_payment');
+					}
+				}
+
 				// Security protection:
 				if ($currencyCodeType && $currencyCodeType != $conf->currency) {	// Check that currency is the good one
 					$error++;
diff --git a/htdocs/public/project/suggestbooth.php b/htdocs/public/project/suggestbooth.php
index c0bcdc751c6..39c2a57700e 100644
--- a/htdocs/public/project/suggestbooth.php
+++ b/htdocs/public/project/suggestbooth.php
@@ -19,16 +19,6 @@
  *	\file       htdocs/public/project/suggestbooth.php
  *	\ingroup    member
  *	\brief      Example of form to suggest a booth
- *
- *  Note that you can add following constant to change behaviour of page
- *  MEMBER_NEWFORM_AMOUNT               Default amount for auto-subscribe form
- *  MEMBER_NEWFORM_EDITAMOUNT           0 or 1 = Amount can be edited
- *  MEMBER_NEWFORM_PAYONLINE            Suggest payment with paypal, paybox or stripe
- *  MEMBER_NEWFORM_DOLIBARRTURNOVER     Show field turnover (specific for dolibarr foundation)
- *  MEMBER_URL_REDIRECT_SUBSCRIPTION    Url to redirect once subscribe submitted
- *  MEMBER_NEWFORM_FORCETYPE            Force type of member
- *  MEMBER_NEWFORM_FORCEMORPHY          Force nature of member (mor/phy)
- *  MEMBER_NEWFORM_FORCECOUNTRYCODE     Force country
  */
 
 if (!defined('NOLOGIN')) {
diff --git a/htdocs/public/project/suggestconference.php b/htdocs/public/project/suggestconference.php
index f2a919c0aa2..b97777c3a9a 100644
--- a/htdocs/public/project/suggestconference.php
+++ b/htdocs/public/project/suggestconference.php
@@ -19,16 +19,6 @@
  *	\file       htdocs/public/project/suggestconference.php
  *	\ingroup    member
  *	\brief      Example of form to suggest a conference
- *
- *  Note that you can add following constant to change behaviour of page
- *  MEMBER_NEWFORM_AMOUNT               Default amount for auto-subscribe form
- *  MEMBER_NEWFORM_EDITAMOUNT           0 or 1 = Amount can be edited
- *  MEMBER_NEWFORM_PAYONLINE            Suggest payment with paypal, paybox or stripe
- *  MEMBER_NEWFORM_DOLIBARRTURNOVER     Show field turnover (specific for dolibarr foundation)
- *  MEMBER_URL_REDIRECT_SUBSCRIPTION    Url to redirect once subscribe submitted
- *  MEMBER_NEWFORM_FORCETYPE            Force type of member
- *  MEMBER_NEWFORM_FORCEMORPHY          Force nature of member (mor/phy)
- *  MEMBER_NEWFORM_FORCECOUNTRYCODE     Force country
  */
 
 if (!defined('NOLOGIN')) {