Speeding up Magento (evil extensions)

Speeding up magentoSpeeding up Magento is the headache of many shop owners, which usually contact us frustrated after seeing how their page loads are way above the market average, causing a really high bounce rate.

Last week, we were tasked to investigate some spikes in a website that were even temporarily bringing the server down in some cases. Thankfully, our customer had Newrelic, which was very helpful pointing us to the right direction.

Tinkering around within Newrelic, we noticed quite a few issues:

  • It was a multi-website shop, with four different domains. One of them had the “shell” folder had directory listing enabled, and some malware/malicious attempt/bot had been crawling it and calling multiple times a php script that performs heavy operations, and was taking nearly 30 minutes to finish.
  • There quite a few 404 entries in newrelic with a load time suspiciously high.
  • There were also some other pages with an abnormally high load time, and they were all coming from the same user agent, also the 404 ones, which seemed to be some sort of SQL injection attempts by the looks of the URLs:


Which url-decoded looks like:

/checkout/-1" OR 3+936-936-1=0+0+0+1 -- /add/uenc/aHR0cDovL3Nob3AuZ2Zpbml0eS5uZXQvb3RoZXItc3R1ZmYuaHRtbA,,/product/13953/form_key/5kBBRqrthVBCRE1e
/category-name/subcategory/shop%' AND 2+1-1-1=0+0+0+1 AND 'FAEs'!='FAEs%/custom-filter/custom-filter-2.html

Then, we started looking at the stack traces, and spotted a third party extension which was the slowest part of execution flow:

Slowest componentsCountDuration%
QuBit_UniversalVariable_Model_Uv::_getLineItems111,100 ms31%

A quick look at the code confirmed our suspicions, we had stumbled upon with another evil magento extension.

The third party extension had an observer on the basket that for each item, was loading the product, and for each product, it was loading each of its assigned categories, with the purpose of generating a JSON file for tracking purposes. It was running “fine” with low traffic, and with a low amount of items in the basket, but the load time was growing exponentially was new products were added to the basket, with together with a malicious behaviour adding over 400 products, was capable of bringing the server down. Interestingly, the tracking code was only required for the checkout cart page, but it was actually running on every single page, which is why the 404 and other non-cached pages were affected.

We deactivated the quotes with over 200 products in the basket (ie. not real users), did a few amendments in the code and deployed the changes. Below you can see the result:

Speeding up magento

A massive drop in the average response time, and guess what? the spikes problems disappeared 🙂

Once again, please be aware of the risks of installing third party extensions in your store, as they can really hinder the user experience of your customers and damage your business.

If you are facing similar problems with your store, do not hesitate to get in touch.

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