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Questions tagged [regex]

security concerns around regular expressions; using them as security-critical filters, processing user-supplied regexes, vulnerabilities in regex parsers, etc.

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Is it a good idea to implement an XSS blocking middleware like cloudflare? [closed]

I noticed that whenever someone tries to send XSS data, Cloudflare blocks it. So I tested it and concluded the pattern. I want to implement a Regex that detects any XSS pattern and block it. Note: I ...
a_duck's user avatar
  • 1
0 votes
4 answers
183 views

How to bypass regex block of request?

I was asked the following question at a job interview recently: You need to reach a web server at the IP address 20.21.22.23 via browser using HTTP. Browser checks the IP address and blocks requests ...
S_I's user avatar
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0 answers
228 views

Stopping a Subscription Bomb

Are there any methods for stopping a subscription bomb other than issuing a new email address? Creating gmail filters is only getting us so far as there are more emails coming in than we can keep up ...
dzzl's user avatar
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2 votes
2 answers
5k views

How do I bypass a regex filter that filters all html to avoid xss?

How do I bypass a regex filter that filters all html to avoid xss? I've tried using things like <img src="aa" onerror="alert(1)"> but still no luck. This is for a CTF ...
ctfhard's user avatar
  • 21
0 votes
2 answers
2k views

Is it possible to exploit preg_match similar to preg_replace PHP? [closed]

I'm currently working on a website and want to prevent characters being inputted, i am using following code if (!preg_match("/^[a-zA-Z0-9_!,()& -\/]*$/" is it possible to exploit this ...
Anon's user avatar
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1 vote
3 answers
821 views

Mailcleaner - Fail2ban - mc-exim-filter configuration

I'm using Fail2ban on a Mailcleaner server which works pretty good, but I want to update it to ban hosts who want to spoof our addresses. I'm using the "original" mc-exim-filter, but I don't ...
Krisztian's user avatar
3 votes
1 answer
826 views

Email pattern ReDoS

I would like to verify that the input from the user complies to the format of email address (in Java application). On the following page there is verbose regex that should properly validate the email ...
RenatoIvancic's user avatar
0 votes
1 answer
3k views

Source of RegEx examples of Secret Detection patterns in repositories?

Where can I find RegEx that can pattern match common secret strings? I have a product that scans repos and commits and in case a developer tries to commit a secret (i.e. passwords, keys). It scans for ...
QuantenGhost's user avatar
1 vote
1 answer
1k views

Possible to bypass this regex for XSS?

When testing for XSS, is it at all possible to bypass the below regex? I doubt it because it only accepts uppercase and lowercase letters, but maybe? /^[A-Za-z]+$/
Jordan Baron's user avatar
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0 answers
107 views

Is it safe to pass user input through rails gsub?

Are there risks associated with using gsub on user input? Can it be used for regular expression DoS?
Tim Abell's user avatar
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1 vote
0 answers
257 views

Regex DoS: Is OWASP's characterization of "evil regexes" complete?

OWASP defines "evil regex" (here) as follows: Evil Regexes A Regex is called "evil" if it can stuck on crafted input. Evil Regex pattern contains: Grouping with repetition ...
Shuzheng's user avatar
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1 answer
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What is the following regex trying to protect against?

I am looking at a Java web application that compares all incoming request params and cookies against the following regex. If it matches, it is considered "an attack" and refuses the request. I'm ...
secondbreakfast's user avatar
2 votes
0 answers
3k views

OAuth access token/API key patterns for large web sites

First off, let me preface this post by saying I'm not a security expert. I'm trying to build regular expressions to find OAuth 2.0 access tokens and API Keys for common web sites such as Google, ...
Geoff Williams's user avatar
0 votes
0 answers
764 views

What is the risk of allowing user input in Python's 're' module

Some context I'm currently building an application which lets user's set up dynamic, queries they can execute later. A great addition to this seems like a regex module, in which users can filter ...
Paradoxis's user avatar
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0 answers
4k views

Boolean blind SQLi with sqlmap

I am trying to run sqlmap in order to find a flag for a CTF. The injection string is sent via a POST request in the parameter called search. The response is received as either 1, 2, or 3 (error codes),...
user209814's user avatar
2 votes
0 answers
263 views

Can a Regex without characters [(+*{}? be dangerous?

I want to create some functionality for non dangerous regex. I want to accept only very few regex cases where it is safe to assume that they are not malicious (but still giving the user some ...
Fabian Enrique Gutierrez's user avatar
0 votes
1 answer
113 views

How to filter HTML Event in Native PHP7

i want to creating xss filter for my own project, this is for html event filtering preg_replace("/ on\w+='[^']*'/i", '', preg_replace('/ on\w+="[^"]*"/i', '', $framed)); but considering to more ...
Reyhan Fabiano's user avatar
1 vote
1 answer
446 views

Is this regular expression vulnerable to DoS?

FindBugs flagged the following email address validation regex as vulnerable to DoS: ^[\w!#$%&'*+/=?`{|}~^-]+(?:\.[\w!#$%&'*+/=?`{|}~^-]+)*@(?:[a-zA-Z0-9-]+\.)+[a-zA-Z]{2,6}$ Here's an easier ...
Duncan Jones's user avatar
  • 1,647
42 votes
7 answers
42k views

Is it possible to detect 100% of SQLi with a simple regex?

I'm wondering if it is possible to detect 100% of the possible SQLi attacks using a simple regex. In other words, using very simple PHP code as an example: if (preg_match("/select/i", $input)) { ...
reed's user avatar
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1 vote
3 answers
3k views

What are the common features to identify Brute-Force attack from Apache log file?

There are various methods to find attack patterns for different types of attacks. Apache-scalp is one such tool, but the rule set is not available to find the brute-force attack pattern via regular ...
Uday's user avatar
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1 vote
1 answer
224 views

Alternative forms for special characters in terminal

I was solving a problem on a popular hacking for fun website, when I got following idea: Is it possible to represent - for example a '/' (just the slash) in the terminal (linux) in another way - for ...
OcK's user avatar
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96 votes
6 answers
21k views

Is it safe to let a user type a regex as a search input?

I was in a mall a few days ago and I searched for a shop on an indication panel. Out of curiosity, I tried a search with (.+) and was a bit surprised to get the list of all the shops in the mall. I'...
Xavier59's user avatar
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2 votes
0 answers
2k views

Brute force hex password with exactly two special characters using JohnTheRipper

I want to optimize the way I'm using John the Ripper. I have a password with a know length (9) that consists only of (lower-case) hex characters and exactly two special characters. First I tried ...
Norbert's user avatar
  • 121